fix(clerk-js): Prevent duplicate __client_uat cookies in iframe contexts#7875

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Merged
brkalow merged 4 commits into from
Feb 18, 2026
Merged

fix(clerk-js): Prevent duplicate __client_uat cookies in iframe contexts #7875

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306e463
fix(clerk-js): Prevent duplicate __client_uat cookies in iframe contexts
brkalow Feb 18, 2026
e4b2d6f
Apply suggestion from @brkalow
brkalow Feb 18, 2026
dc611ff
fix(clerk-js): Pass SameSite/Secure attributes to eTLD+1 cookie probe
brkalow Feb 18, 2026
b245c99
dedupe
brkalow Feb 18, 2026
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5 changes: 5 additions & 0 deletions .changeset/fix-iframe-client-uat-cookie-domain.md
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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
---
'@clerk/clerk-js': patch
---

Fix `__client_uat` cookie being set on two different domain scopes when app is loaded in both iframe and non-iframe contexts. `getCookieDomain()` now falls back to `hostname` instead of `undefined` when the eTLD+1 probe fails, and the eTLD+1 probe uses the same `SameSite`/`Secure` attributes as the actual cookie to ensure consistent behavior across contexts.
17 changes: 15 additions & 2 deletions packages/clerk-js/src/core/auth/__tests__/getCookieDomain.test.ts
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Original file line numberDiff line numberDiff line change
Expand Up@@ -35,6 +35,19 @@ describe('getCookieDomain', () => {
expect(result).toBe(hostname);
});

it('passes cookie attributes to the probe', () => {
const hostname = 'app.example.com';
const handler: CookieHandler = {
get: vi.fn().mockReturnValueOnce(undefined).mockReturnValueOnce('1'),
set: vi.fn().mockReturnValue(undefined),
remove: vi.fn().mockReturnValue(undefined),
};
const attrs = { sameSite: 'None', secure: true };
getCookieDomain(hostname, handler, attrs);
expect(handler.set).toHaveBeenCalledWith('1', { sameSite: 'None', secure: true, domain: 'example.com' });
expect(handler.set).toHaveBeenCalledWith('1', { sameSite: 'None', secure: true, domain: 'app.example.com' });
});

it('handles localhost', () => {
const hostname = 'localhost';
const result = getCookieDomain(hostname);
Expand All@@ -53,15 +66,15 @@ describe('getCookieDomain', () => {
expect(getCookieDomain('bryce-local')).toBe('bryce-local');
});

it('returns undefined if the domain could not be determined', () => {
it('falls back to hostname if the domain could not be determined', () => {
const handler: CookieHandler = {
get: vi.fn().mockReturnValue(undefined),
set: vi.fn().mockReturnValue(undefined),
remove: vi.fn().mockReturnValue(undefined),
};
const hostname = 'app.hello.co.uk';
const result = getCookieDomain(hostname, handler);
expect(result).toBeUndefined();
expect(result).toBe(hostname);
});

it('uses cached value if there is one', () => {
Expand Down
2 changes: 1 addition & 1 deletion packages/clerk-js/src/core/auth/cookies/clientUat.ts
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Original file line numberDiff line numberDiff line change
Expand Up@@ -45,7 +45,7 @@ export const createClientUatCookie = (cookieSuffix: string): ClientUatCookieHand
: 'Strict';
const secure = getSecureAttribute(sameSite);
const partitioned = __BUILD_VARIANT_CHIPS__ && secure;
const domain = getCookieDomain();
const domain = getCookieDomain(undefined, undefined, { sameSite, secure });

// '0' indicates the user is signed out
let val = '0';
Expand Down
27 changes: 22 additions & 5 deletions packages/clerk-js/src/core/auth/getCookieDomain.ts
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Original file line numberDiff line numberDiff line change
Expand Up@@ -8,7 +8,19 @@ import { createCookieHandler } from '@clerk/shared/cookie';
let cachedETLDPlusOne: string;
const eTLDCookie = createCookieHandler('__clerk_test_etld');

export function getCookieDomain(hostname = window.location.hostname, cookieHandler = eTLDCookie) {
/**
* @param hostname - The hostname to determine the eTLD+1 for.
* @param cookieHandler - The cookie handler to use for the eTLD+1 probe.
* @param cookieAttributes - Optional cookie attributes (sameSite, secure) to use
* during the eTLD+1 probe. These should match the attributes that will be used
* when setting the actual cookie, so the probe accurately reflects whether a
* domain-scoped cookie can be set in the current context.
*/
export function getCookieDomain(
hostname = window.location.hostname,
cookieHandler = eTLDCookie,
cookieAttributes?: { sameSite?: string; secure?: boolean },
) {
Comment on lines +11 to +23

@coderabbitaicoderabbitaiBotFeb 18, 2026

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⚠️ Potential issue | 🟠 Major

🧩 Analysis chain

🏁 Script executed:

cat -n packages/clerk-js/src/core/auth/getCookieDomain.ts

Repository: clerk/javascript

Length of output: 2746

Add explicit return type and complete JSDoc documentation for the exported getCookieDomain function.

This public API lacks an explicit return type annotation. Its JSDoc documentation is also incomplete, missing @returns, @throws, and @example tags required by the TypeScript and JSDoc guidelines.

Suggested patch
 /**
* `@param` hostname - The hostname to determine the eTLD+1 for.
* `@param` cookieHandler - The cookie handler to use for the eTLD+1 probe.
* `@param` cookieAttributes - Optional cookie attributes (sameSite, secure) to use
* during the eTLD+1 probe. These should match the attributes that will be used
* when setting the actual cookie, so the probe accurately reflects whether a
* domain-scoped cookie can be set in the current context.
+ * `@returns` The resolved eTLD+1 domain to use for setting cookies.+ * `@throws` If the cookie handler throws while probing domains.+ * `@example`+ * getCookieDomain('app.example.com', undefined, { sameSite: 'None', secure: true });
*/
export function getCookieDomain(
hostname = window.location.hostname,
cookieHandler = eTLDCookie,
cookieAttributes?: { sameSite?: string; secure?: boolean },
-) {+): string {
📝 Committable suggestion

‼️IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change
/**
* @paramhostname-ThehostnametodeterminetheeTLD+1for.
* @paramcookieHandler-ThecookiehandlertousefortheeTLD+1probe.
* @paramcookieAttributes-Optionalcookieattributes(sameSite,secure)touse
*duringtheeTLD+1probe.Theseshouldmatchtheattributesthatwillbeused
*whensettingtheactualcookie,sotheprobeaccuratelyreflectswhethera
*domain-scopedcookiecanbesetinthecurrentcontext.
*/
exportfunctiongetCookieDomain(
hostname=window.location.hostname,
cookieHandler=eTLDCookie,
cookieAttributes?: {sameSite?: string; secure?: boolean},
){
/**
*`@param`hostname-ThehostnametodeterminetheeTLD+1for.
*`@param`cookieHandler-ThecookiehandlertousefortheeTLD+1probe.
*`@param`cookieAttributes-Optionalcookieattributes(sameSite,secure)touse
*duringtheeTLD+1probe.Theseshouldmatchtheattributesthatwillbeused
*whensettingtheactualcookie,sotheprobeaccuratelyreflectswhethera
*domain-scopedcookiecanbesetinthecurrentcontext.
*`@returns`TheresolvedeTLD+1domaintouseforsettingcookies.
*`@throws`Ifthecookiehandlerthrowswhileprobingdomains.
*`@example`
*getCookieDomain('app.example.com',undefined,{sameSite: 'None',secure: true});
*/
exportfunctiongetCookieDomain(
hostname=window.location.hostname,
cookieHandler=eTLDCookie,
cookieAttributes?: {sameSite?: string; secure?: boolean},
): string {
🤖 Prompt for AI Agents
Verify each finding against the current code and only fix it if needed.
In `@packages/clerk-js/src/core/auth/getCookieDomain.ts` around lines 11 - 23, The
exported function getCookieDomain lacks an explicit TypeScript return type and
its JSDoc is incomplete; update the declaration of getCookieDomain to include an
explicit return type (e.g., string | undefined) and ensure cookieAttributes has
precise types (sameSite?: 'Lax' | 'Strict' | 'None' | string; secure?: boolean),
then expand the JSDoc for getCookieDomain to include `@returns` describing the
returned eTLD+1 or undefined, `@throws` describing any errors thrown during the
eTLD+1 probe (e.g., when cookie handling fails), and an `@example` showing typical
usage; reference the function name getCookieDomain and the cookieAttributes
param as the places to change.

// only compute it once per session to avoid unnecessary cookie ops
if (cachedETLDPlusOne) {
return cachedETLDPlusOne;
Expand All@@ -28,17 +40,22 @@ export function getCookieDomain(hostname = window.location.hostname, cookieHandl
// we know for sure that the first entry is definitely a TLD, skip it
for (let i = hostnameParts.length - 2; i >= 0; i--) {
const eTLD = hostnameParts.slice(i).join('.');
cookieHandler.set('1', { domain: eTLD });
cookieHandler.set('1', { ...cookieAttributes, domain: eTLD });

const res = cookieHandler.get();
if (res === '1') {
cookieHandler.remove({ domain: eTLD });
cookieHandler.remove({ ...cookieAttributes, domain: eTLD });
cachedETLDPlusOne = eTLD;
return eTLD;
}

cookieHandler.remove({ domain: eTLD });
cookieHandler.remove({ ...cookieAttributes, domain: eTLD });
}

return;
// Fallback to hostname to ensure domain-scoped cookie rather than host-only.
// In restricted contexts (e.g. cross-origin iframes), the set() will silently
// fail — which is preferable to creating a host-only cookie that conflicts
// with domain-scoped cookies set by non-iframe contexts.
cachedETLDPlusOne = hostname;

@jacekradkojacekradkoFeb 18, 2026

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Hmm. I think it makes sense, but I wonder if this could potentially set a cookie on a different subdomain that would still create 2 separate cookies in some cases. 🤔

return hostname;
}
45 changes: 43 additions & 2 deletions pnpm-lock.yaml
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Open in desktop

Some generated files are not rendered by default. Learn more about how customized files appear on GitHub.

, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Add copy buttons to all 
 blocks\n(function() {\n function addCopyButtons() {\n document.querySelectorAll('pre code').forEach(function(codeBlock) {\n if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;\n codeBlock.parentElement.setAttribute('data-copy-added', 'true');\n \n var btn = document.createElement('button');\n btn.textContent = 'Copy';\n btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';\n btn.onmouseover = function() { this.style.opacity = '1'; };\n btn.onmouseout = function() { this.style.opacity = '0.7'; };\n btn.onclick = function() {\n navigator.clipboard.writeText(codeBlock.textContent).then(function() {\n btn.textContent = 'Copied!';\n setTimeout(function() { btn.textContent = 'Copy'; }, 1500);\n });\n };\n codeBlock.parentElement.style.position = 'relative';\n codeBlock.parentElement.appendChild(btn);\n });\n }\n \n addCopyButtons();\n \n // Re-run on dynamic content\n var observer = new MutationObserver(addCopyButtons);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Add Copy Buttons to Code Blocks");
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '

Skip to content
fix(clerk-js): Prevent duplicate __client_uat cookies in iframe contexts#7875

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to your account

 Merged

brkalow
merged 4 commits into

from

Feb 18, 2026
 Merged


fix(clerk-js): Prevent duplicate __client_uat cookies in iframe contexts
#7875
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306e463

fix(clerk-js): Prevent duplicate __client_uat cookies in iframe contexts


brkalow Feb 18, 2026
e4b2d6f

Apply suggestion from @brkalow


brkalow Feb 18, 2026
dc611ff

fix(clerk-js): Pass SameSite/Secure attributes to eTLD+1 cookie probe


brkalow Feb 18, 2026
b245c99

dedupe


brkalow Feb 18, 2026

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5 changes: 5 additions & 0 deletions
.changeset/fix-iframe-client-uat-cookie-domain.md

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
---
'@clerk/clerk-js': patch
---

Fix `__client_uat` cookie being set on two different domain scopes when app is loaded in both iframe and non-iframe contexts. `getCookieDomain()` now falls back to `hostname` instead of `undefined` when the eTLD+1 probe fails, and the eTLD+1 probe uses the same `SameSite`/`Secure` attributes as the actual cookie to ensure consistent behavior across contexts.

17 changes: 15 additions & 2 deletions
packages/clerk-js/src/core/auth/__tests__/getCookieDomain.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -35,6 +35,19 @@ describe('getCookieDomain', () => {
 expect(result).toBe(hostname);
 });

 it('passes cookie attributes to the probe', () => {
 const hostname = 'app.example.com';
 const handler: CookieHandler = {
 get: vi.fn().mockReturnValueOnce(undefined).mockReturnValueOnce('1'),
 set: vi.fn().mockReturnValue(undefined),
 remove: vi.fn().mockReturnValue(undefined),
 };
 const attrs = { sameSite: 'None', secure: true };
 getCookieDomain(hostname, handler, attrs);
 expect(handler.set).toHaveBeenCalledWith('1', { sameSite: 'None', secure: true, domain: 'example.com' });
 expect(handler.set).toHaveBeenCalledWith('1', { sameSite: 'None', secure: true, domain: 'app.example.com' });
 });

 it('handles localhost', () => {
 const hostname = 'localhost';
 const result = getCookieDomain(hostname);
Expand All@@ -53,15 +66,15 @@ describe('getCookieDomain', () => {
 expect(getCookieDomain('bryce-local')).toBe('bryce-local');
 });

 it('returns undefined if the domain could not be determined', () => {
 it('falls back to hostname if the domain could not be determined', () => {
 const handler: CookieHandler = {
 get: vi.fn().mockReturnValue(undefined),
 set: vi.fn().mockReturnValue(undefined),
 remove: vi.fn().mockReturnValue(undefined),
 };
 const hostname = 'app.hello.co.uk';
 const result = getCookieDomain(hostname, handler);
 expect(result).toBeUndefined();
 expect(result).toBe(hostname);
 });

 it('uses cached value if there is one', () => {
Expand Down

2 changes: 1 addition & 1 deletion
packages/clerk-js/src/core/auth/cookies/clientUat.ts

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Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -45,7 +45,7 @@ export const createClientUatCookie = (cookieSuffix: string): ClientUatCookieHand
 : 'Strict';
 const secure = getSecureAttribute(sameSite);
 const partitioned = __BUILD_VARIANT_CHIPS__ && secure;
 const domain = getCookieDomain();
 const domain = getCookieDomain(undefined, undefined, { sameSite, secure });

 // '0' indicates the user is signed out
 let val = '0';
Expand Down

27 changes: 22 additions & 5 deletions
packages/clerk-js/src/core/auth/getCookieDomain.ts

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Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -8,7 +8,19 @@ import { createCookieHandler } from '@clerk/shared/cookie';
let cachedETLDPlusOne: string;
const eTLDCookie = createCookieHandler('__clerk_test_etld');

export function getCookieDomain(hostname = window.location.hostname, cookieHandler = eTLDCookie) {
/**
 * @param hostname - The hostname to determine the eTLD+1 for.
 * @param cookieHandler - The cookie handler to use for the eTLD+1 probe.
 * @param cookieAttributes - Optional cookie attributes (sameSite, secure) to use
 * during the eTLD+1 probe. These should match the attributes that will be used
 * when setting the actual cookie, so the probe accurately reflects whether a
 * domain-scoped cookie can be set in the current context.
 */
export function getCookieDomain(
 hostname = window.location.hostname,
 cookieHandler = eTLDCookie,
 cookieAttributes?: { sameSite?: string; secure?: boolean },
) {

Comment on lines

+11
 to 
+23

@coderabbitaicoderabbitaiBotFeb 18, 2026

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⚠️ Potential issue | 🟠 Major
🧩 Analysis chain
🏁 Script executed:
cat -n packages/clerk-js/src/core/auth/getCookieDomain.ts
Repository: clerk/javascript
Length of output: 2746
Add explicit return type and complete JSDoc documentation for the exported getCookieDomain function.
This public API lacks an explicit return type annotation. Its JSDoc documentation is also incomplete, missing @returns, @throws, and @example tags required by the TypeScript and JSDoc guidelines.
Suggested patch
 /**
* `@param` hostname - The hostname to determine the eTLD+1 for.
* `@param` cookieHandler - The cookie handler to use for the eTLD+1 probe.
* `@param` cookieAttributes - Optional cookie attributes (sameSite, secure) to use
* during the eTLD+1 probe. These should match the attributes that will be used
* when setting the actual cookie, so the probe accurately reflects whether a
* domain-scoped cookie can be set in the current context.
+ * `@returns` The resolved eTLD+1 domain to use for setting cookies.+ * `@throws` If the cookie handler throws while probing domains.+ * `@example`+ * getCookieDomain('app.example.com', undefined, { sameSite: 'None', secure: true });
*/
export function getCookieDomain(
hostname = window.location.hostname,
cookieHandler = eTLDCookie,
cookieAttributes?: { sameSite?: string; secure?: boolean },
-) {+): string {
📝 Committable suggestion
‼️IMPORTANT

Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change

/**
* @paramhostname-ThehostnametodeterminetheeTLD+1for.
* @paramcookieHandler-ThecookiehandlertousefortheeTLD+1probe.
* @paramcookieAttributes-Optionalcookieattributes(sameSite,secure)touse
*duringtheeTLD+1probe.Theseshouldmatchtheattributesthatwillbeused
*whensettingtheactualcookie,sotheprobeaccuratelyreflectswhethera
*domain-scopedcookiecanbesetinthecurrentcontext.
*/
exportfunctiongetCookieDomain(
hostname=window.location.hostname,
cookieHandler=eTLDCookie,
 cookieAttributes?: {sameSite?: string; secure?: boolean},
){
/**
*`@param`hostname-ThehostnametodeterminetheeTLD+1for.
*`@param`cookieHandler-ThecookiehandlertousefortheeTLD+1probe.
*`@param`cookieAttributes-Optionalcookieattributes(sameSite,secure)touse
*duringtheeTLD+1probe.Theseshouldmatchtheattributesthatwillbeused
*whensettingtheactualcookie,sotheprobeaccuratelyreflectswhethera
*domain-scopedcookiecanbesetinthecurrentcontext.
*`@returns`TheresolvedeTLD+1domaintouseforsettingcookies.
*`@throws`Ifthecookiehandlerthrowswhileprobingdomains.
*`@example`
*getCookieDomain('app.example.com',undefined,{sameSite: 'None',secure: true});
*/
exportfunctiongetCookieDomain(
hostname=window.location.hostname,
cookieHandler=eTLDCookie,
 cookieAttributes?: {sameSite?: string; secure?: boolean},
): string {
🤖 Prompt for AI Agents
Verify each finding against the current code and only fix it if needed.
In `@packages/clerk-js/src/core/auth/getCookieDomain.ts` around lines 11 - 23, The
exported function getCookieDomain lacks an explicit TypeScript return type and
its JSDoc is incomplete; update the declaration of getCookieDomain to include an
explicit return type (e.g., string | undefined) and ensure cookieAttributes has
precise types (sameSite?: 'Lax' | 'Strict' | 'None' | string; secure?: boolean),
then expand the JSDoc for getCookieDomain to include `@returns` describing the
returned eTLD+1 or undefined, `@throws` describing any errors thrown during the
eTLD+1 probe (e.g., when cookie handling fails), and an `@example` showing typical
usage; reference the function name getCookieDomain and the cookieAttributes
param as the places to change.

 // only compute it once per session to avoid unnecessary cookie ops
 if (cachedETLDPlusOne) {
 return cachedETLDPlusOne;
Expand All@@ -28,17 +40,22 @@ export function getCookieDomain(hostname = window.location.hostname, cookieHandl
 // we know for sure that the first entry is definitely a TLD, skip it
 for (let i = hostnameParts.length - 2; i >= 0; i--) {
 const eTLD = hostnameParts.slice(i).join('.');
 cookieHandler.set('1', { domain: eTLD });
 cookieHandler.set('1', { ...cookieAttributes, domain: eTLD });

 const res = cookieHandler.get();
 if (res === '1') {
 cookieHandler.remove({ domain: eTLD });
 cookieHandler.remove({ ...cookieAttributes, domain: eTLD });
 cachedETLDPlusOne = eTLD;
 return eTLD;
 }

 cookieHandler.remove({ domain: eTLD });
 cookieHandler.remove({ ...cookieAttributes, domain: eTLD });
 }

 return;
 // Fallback to hostname to ensure domain-scoped cookie rather than host-only.
 // In restricted contexts (e.g. cross-origin iframes), the set() will silently
 // fail — which is preferable to creating a host-only cookie that conflicts
 // with domain-scoped cookies set by non-iframe contexts.
 cachedETLDPlusOne = hostname;
@jacekradkojacekradkoFeb 18, 2026

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Choose a reason for hiding this comment

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Hmm. I think it makes sense, but I wonder if this could potentially set a cookie on a different subdomain that would still create 2 separate cookies in some cases. 🤔
 return hostname;
}

45 changes: 43 additions & 2 deletions
pnpm-lock.yaml

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Some generated files are not rendered by default. Learn more about how customized files appear on GitHub.


, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Force GitHub README to respect dark mode\n(function() {\n var style = document.createElement('style');\n style.textContent = '\n .markdown-body {\n color-scheme: dark light;\n }\n .markdown-body pre { background: #161b22 !important; }\n .markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }\n .markdown-body table th, .markdown-body table td { border-color: #30363d !important; }\n .markdown-body img { background: #0d1117; }\n .markdown-body blockquote { border-left-color: #8b949e; }\n .markdown-body hr { border-color: #30363d; }\n ';\n document.head.appendChild(style);\n})();", "GitHub Dark Mode README Fix");
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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fix(clerk-js): Prevent duplicate __client_uat cookies in iframe contexts#7875

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Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

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 Merged

brkalow
merged 4 commits into

from

Feb 18, 2026
 Merged


fix(clerk-js): Prevent duplicate __client_uat cookies in iframe contexts
#7875
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306e463

fix(clerk-js): Prevent duplicate __client_uat cookies in iframe contexts


brkalow Feb 18, 2026
e4b2d6f

Apply suggestion from @brkalow


brkalow Feb 18, 2026
dc611ff

fix(clerk-js): Pass SameSite/Secure attributes to eTLD+1 cookie probe


brkalow Feb 18, 2026
b245c99

dedupe


brkalow Feb 18, 2026

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5 changes: 5 additions & 0 deletions
.changeset/fix-iframe-client-uat-cookie-domain.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
---
'@clerk/clerk-js': patch
---

Fix `__client_uat` cookie being set on two different domain scopes when app is loaded in both iframe and non-iframe contexts. `getCookieDomain()` now falls back to `hostname` instead of `undefined` when the eTLD+1 probe fails, and the eTLD+1 probe uses the same `SameSite`/`Secure` attributes as the actual cookie to ensure consistent behavior across contexts.

17 changes: 15 additions & 2 deletions
packages/clerk-js/src/core/auth/__tests__/getCookieDomain.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -35,6 +35,19 @@ describe('getCookieDomain', () => {
 expect(result).toBe(hostname);
 });

 it('passes cookie attributes to the probe', () => {
 const hostname = 'app.example.com';
 const handler: CookieHandler = {
 get: vi.fn().mockReturnValueOnce(undefined).mockReturnValueOnce('1'),
 set: vi.fn().mockReturnValue(undefined),
 remove: vi.fn().mockReturnValue(undefined),
 };
 const attrs = { sameSite: 'None', secure: true };
 getCookieDomain(hostname, handler, attrs);
 expect(handler.set).toHaveBeenCalledWith('1', { sameSite: 'None', secure: true, domain: 'example.com' });
 expect(handler.set).toHaveBeenCalledWith('1', { sameSite: 'None', secure: true, domain: 'app.example.com' });
 });

 it('handles localhost', () => {
 const hostname = 'localhost';
 const result = getCookieDomain(hostname);
Expand All@@ -53,15 +66,15 @@ describe('getCookieDomain', () => {
 expect(getCookieDomain('bryce-local')).toBe('bryce-local');
 });

 it('returns undefined if the domain could not be determined', () => {
 it('falls back to hostname if the domain could not be determined', () => {
 const handler: CookieHandler = {
 get: vi.fn().mockReturnValue(undefined),
 set: vi.fn().mockReturnValue(undefined),
 remove: vi.fn().mockReturnValue(undefined),
 };
 const hostname = 'app.hello.co.uk';
 const result = getCookieDomain(hostname, handler);
 expect(result).toBeUndefined();
 expect(result).toBe(hostname);
 });

 it('uses cached value if there is one', () => {
Expand Down

2 changes: 1 addition & 1 deletion
packages/clerk-js/src/core/auth/cookies/clientUat.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -45,7 +45,7 @@ export const createClientUatCookie = (cookieSuffix: string): ClientUatCookieHand
 : 'Strict';
 const secure = getSecureAttribute(sameSite);
 const partitioned = __BUILD_VARIANT_CHIPS__ && secure;
 const domain = getCookieDomain();
 const domain = getCookieDomain(undefined, undefined, { sameSite, secure });

 // '0' indicates the user is signed out
 let val = '0';
Expand Down

27 changes: 22 additions & 5 deletions
packages/clerk-js/src/core/auth/getCookieDomain.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -8,7 +8,19 @@ import { createCookieHandler } from '@clerk/shared/cookie';
let cachedETLDPlusOne: string;
const eTLDCookie = createCookieHandler('__clerk_test_etld');

export function getCookieDomain(hostname = window.location.hostname, cookieHandler = eTLDCookie) {
/**
 * @param hostname - The hostname to determine the eTLD+1 for.
 * @param cookieHandler - The cookie handler to use for the eTLD+1 probe.
 * @param cookieAttributes - Optional cookie attributes (sameSite, secure) to use
 * during the eTLD+1 probe. These should match the attributes that will be used
 * when setting the actual cookie, so the probe accurately reflects whether a
 * domain-scoped cookie can be set in the current context.
 */
export function getCookieDomain(
 hostname = window.location.hostname,
 cookieHandler = eTLDCookie,
 cookieAttributes?: { sameSite?: string; secure?: boolean },
) {

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⚠️ Potential issue | 🟠 Major
🧩 Analysis chain
🏁 Script executed:
cat -n packages/clerk-js/src/core/auth/getCookieDomain.ts
Repository: clerk/javascript
Length of output: 2746
Add explicit return type and complete JSDoc documentation for the exported getCookieDomain function.
This public API lacks an explicit return type annotation. Its JSDoc documentation is also incomplete, missing @returns, @throws, and @example tags required by the TypeScript and JSDoc guidelines.
Suggested patch
 /**
* `@param` hostname - The hostname to determine the eTLD+1 for.
* `@param` cookieHandler - The cookie handler to use for the eTLD+1 probe.
* `@param` cookieAttributes - Optional cookie attributes (sameSite, secure) to use
* during the eTLD+1 probe. These should match the attributes that will be used
* when setting the actual cookie, so the probe accurately reflects whether a
* domain-scoped cookie can be set in the current context.
+ * `@returns` The resolved eTLD+1 domain to use for setting cookies.+ * `@throws` If the cookie handler throws while probing domains.+ * `@example`+ * getCookieDomain('app.example.com', undefined, { sameSite: 'None', secure: true });
*/
export function getCookieDomain(
hostname = window.location.hostname,
cookieHandler = eTLDCookie,
cookieAttributes?: { sameSite?: string; secure?: boolean },
-) {+): string {
📝 Committable suggestion
‼️IMPORTANT

Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change

/**
* @paramhostname-ThehostnametodeterminetheeTLD+1for.
* @paramcookieHandler-ThecookiehandlertousefortheeTLD+1probe.
* @paramcookieAttributes-Optionalcookieattributes(sameSite,secure)touse
*duringtheeTLD+1probe.Theseshouldmatchtheattributesthatwillbeused
*whensettingtheactualcookie,sotheprobeaccuratelyreflectswhethera
*domain-scopedcookiecanbesetinthecurrentcontext.
*/
exportfunctiongetCookieDomain(
hostname=window.location.hostname,
cookieHandler=eTLDCookie,
 cookieAttributes?: {sameSite?: string; secure?: boolean},
){
/**
*`@param`hostname-ThehostnametodeterminetheeTLD+1for.
*`@param`cookieHandler-ThecookiehandlertousefortheeTLD+1probe.
*`@param`cookieAttributes-Optionalcookieattributes(sameSite,secure)touse
*duringtheeTLD+1probe.Theseshouldmatchtheattributesthatwillbeused
*whensettingtheactualcookie,sotheprobeaccuratelyreflectswhethera
*domain-scopedcookiecanbesetinthecurrentcontext.
*`@returns`TheresolvedeTLD+1domaintouseforsettingcookies.
*`@throws`Ifthecookiehandlerthrowswhileprobingdomains.
*`@example`
*getCookieDomain('app.example.com',undefined,{sameSite: 'None',secure: true});
*/
exportfunctiongetCookieDomain(
hostname=window.location.hostname,
cookieHandler=eTLDCookie,
 cookieAttributes?: {sameSite?: string; secure?: boolean},
): string {
🤖 Prompt for AI Agents
Verify each finding against the current code and only fix it if needed.
In `@packages/clerk-js/src/core/auth/getCookieDomain.ts` around lines 11 - 23, The
exported function getCookieDomain lacks an explicit TypeScript return type and
its JSDoc is incomplete; update the declaration of getCookieDomain to include an
explicit return type (e.g., string | undefined) and ensure cookieAttributes has
precise types (sameSite?: 'Lax' | 'Strict' | 'None' | string; secure?: boolean),
then expand the JSDoc for getCookieDomain to include `@returns` describing the
returned eTLD+1 or undefined, `@throws` describing any errors thrown during the
eTLD+1 probe (e.g., when cookie handling fails), and an `@example` showing typical
usage; reference the function name getCookieDomain and the cookieAttributes
param as the places to change.

 // only compute it once per session to avoid unnecessary cookie ops
 if (cachedETLDPlusOne) {
 return cachedETLDPlusOne;
Expand All@@ -28,17 +40,22 @@ export function getCookieDomain(hostname = window.location.hostname, cookieHandl
 // we know for sure that the first entry is definitely a TLD, skip it
 for (let i = hostnameParts.length - 2; i >= 0; i--) {
 const eTLD = hostnameParts.slice(i).join('.');
 cookieHandler.set('1', { domain: eTLD });
 cookieHandler.set('1', { ...cookieAttributes, domain: eTLD });

 const res = cookieHandler.get();
 if (res === '1') {
 cookieHandler.remove({ domain: eTLD });
 cookieHandler.remove({ ...cookieAttributes, domain: eTLD });
 cachedETLDPlusOne = eTLD;
 return eTLD;
 }

 cookieHandler.remove({ domain: eTLD });
 cookieHandler.remove({ ...cookieAttributes, domain: eTLD });
 }

 return;
 // Fallback to hostname to ensure domain-scoped cookie rather than host-only.
 // In restricted contexts (e.g. cross-origin iframes), the set() will silently
 // fail — which is preferable to creating a host-only cookie that conflicts
 // with domain-scoped cookies set by non-iframe contexts.
 cachedETLDPlusOne = hostname;
@jacekradkojacekradkoFeb 18, 2026

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Hmm. I think it makes sense, but I wonder if this could potentially set a cookie on a different subdomain that would still create 2 separate cookies in some cases. 🤔
 return hostname;
}

45 changes: 43 additions & 2 deletions
pnpm-lock.yaml

View file


Open in desktop


Some generated files are not rendered by default. Learn more about how customized files appear on GitHub.


, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Highlight search terms from Google/DuckDuckGo/Bing referrer\n(function() {\n var ref = document.referrer;\n var terms = [];\n \n if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {\n var url = new URL(ref);\n var q = url.searchParams.get('q') || url.searchParams.get('p');\n if (q) {\n terms = q.split(/\\s+/).filter(function(t) { return t.length > 2; });\n }\n }\n \n if (terms.length === 0) return;\n \n var style = document.createElement('style');\n style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';\n document.head.appendChild(style);\n \n function highlight(node) {\n if (node.nodeType === 3) { // text node\n var text = node.textContent;\n var found = false;\n terms.forEach(function(term) {\n var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\\]\\\\]/g, '\\\\') + ')', 'gi');\n if (regex.test(text)) {\n found = true;\n var frag = document.createDocumentFragment();\n var parts = text.split(regex);\n parts.forEach(function(part, i) {\n if (i % 2 === 0) {\n frag.appendChild(document.createTextNode(part));\n } else {\n var span = document.createElement('span');\n span.className = 'userscript-highlight';\n span.textContent = part;\n frag.appendChild(span);\n }\n });\n node.parentNode.replaceChild(frag, node);\n }\n });\n } else if (node.nodeType === 1 && node.childNodes) { // element\n var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];\n if (!skipTags.includes(node.tagName)) {\n Array.from(node.childNodes).forEach(highlight);\n }\n }\n }\n \n highlight(document.body);\n \n // Re-highlight on dynamic content\n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1 || node.nodeType === 3) highlight(node);\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Highlight Search Terms");
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
fix(clerk-js): Prevent duplicate __client_uat cookies in iframe contexts#7875

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 Merged

brkalow
merged 4 commits into

from

Feb 18, 2026
 Merged


fix(clerk-js): Prevent duplicate __client_uat cookies in iframe contexts
#7875
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306e463

fix(clerk-js): Prevent duplicate __client_uat cookies in iframe contexts


brkalow Feb 18, 2026
e4b2d6f

Apply suggestion from @brkalow


brkalow Feb 18, 2026
dc611ff

fix(clerk-js): Pass SameSite/Secure attributes to eTLD+1 cookie probe


brkalow Feb 18, 2026
b245c99

dedupe


brkalow Feb 18, 2026

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5 changes: 5 additions & 0 deletions
.changeset/fix-iframe-client-uat-cookie-domain.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
---
'@clerk/clerk-js': patch
---

Fix `__client_uat` cookie being set on two different domain scopes when app is loaded in both iframe and non-iframe contexts. `getCookieDomain()` now falls back to `hostname` instead of `undefined` when the eTLD+1 probe fails, and the eTLD+1 probe uses the same `SameSite`/`Secure` attributes as the actual cookie to ensure consistent behavior across contexts.

17 changes: 15 additions & 2 deletions
packages/clerk-js/src/core/auth/__tests__/getCookieDomain.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -35,6 +35,19 @@ describe('getCookieDomain', () => {
 expect(result).toBe(hostname);
 });

 it('passes cookie attributes to the probe', () => {
 const hostname = 'app.example.com';
 const handler: CookieHandler = {
 get: vi.fn().mockReturnValueOnce(undefined).mockReturnValueOnce('1'),
 set: vi.fn().mockReturnValue(undefined),
 remove: vi.fn().mockReturnValue(undefined),
 };
 const attrs = { sameSite: 'None', secure: true };
 getCookieDomain(hostname, handler, attrs);
 expect(handler.set).toHaveBeenCalledWith('1', { sameSite: 'None', secure: true, domain: 'example.com' });
 expect(handler.set).toHaveBeenCalledWith('1', { sameSite: 'None', secure: true, domain: 'app.example.com' });
 });

 it('handles localhost', () => {
 const hostname = 'localhost';
 const result = getCookieDomain(hostname);
Expand All@@ -53,15 +66,15 @@ describe('getCookieDomain', () => {
 expect(getCookieDomain('bryce-local')).toBe('bryce-local');
 });

 it('returns undefined if the domain could not be determined', () => {
 it('falls back to hostname if the domain could not be determined', () => {
 const handler: CookieHandler = {
 get: vi.fn().mockReturnValue(undefined),
 set: vi.fn().mockReturnValue(undefined),
 remove: vi.fn().mockReturnValue(undefined),
 };
 const hostname = 'app.hello.co.uk';
 const result = getCookieDomain(hostname, handler);
 expect(result).toBeUndefined();
 expect(result).toBe(hostname);
 });

 it('uses cached value if there is one', () => {
Expand Down

2 changes: 1 addition & 1 deletion
packages/clerk-js/src/core/auth/cookies/clientUat.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -45,7 +45,7 @@ export const createClientUatCookie = (cookieSuffix: string): ClientUatCookieHand
 : 'Strict';
 const secure = getSecureAttribute(sameSite);
 const partitioned = __BUILD_VARIANT_CHIPS__ && secure;
 const domain = getCookieDomain();
 const domain = getCookieDomain(undefined, undefined, { sameSite, secure });

 // '0' indicates the user is signed out
 let val = '0';
Expand Down

27 changes: 22 additions & 5 deletions
packages/clerk-js/src/core/auth/getCookieDomain.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -8,7 +8,19 @@ import { createCookieHandler } from '@clerk/shared/cookie';
let cachedETLDPlusOne: string;
const eTLDCookie = createCookieHandler('__clerk_test_etld');

export function getCookieDomain(hostname = window.location.hostname, cookieHandler = eTLDCookie) {
/**
 * @param hostname - The hostname to determine the eTLD+1 for.
 * @param cookieHandler - The cookie handler to use for the eTLD+1 probe.
 * @param cookieAttributes - Optional cookie attributes (sameSite, secure) to use
 * during the eTLD+1 probe. These should match the attributes that will be used
 * when setting the actual cookie, so the probe accurately reflects whether a
 * domain-scoped cookie can be set in the current context.
 */
export function getCookieDomain(
 hostname = window.location.hostname,
 cookieHandler = eTLDCookie,
 cookieAttributes?: { sameSite?: string; secure?: boolean },
) {

Comment on lines

+11
 to 
+23

@coderabbitaicoderabbitaiBotFeb 18, 2026

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⚠️ Potential issue | 🟠 Major
🧩 Analysis chain
🏁 Script executed:
cat -n packages/clerk-js/src/core/auth/getCookieDomain.ts
Repository: clerk/javascript
Length of output: 2746
Add explicit return type and complete JSDoc documentation for the exported getCookieDomain function.
This public API lacks an explicit return type annotation. Its JSDoc documentation is also incomplete, missing @returns, @throws, and @example tags required by the TypeScript and JSDoc guidelines.
Suggested patch
 /**
* `@param` hostname - The hostname to determine the eTLD+1 for.
* `@param` cookieHandler - The cookie handler to use for the eTLD+1 probe.
* `@param` cookieAttributes - Optional cookie attributes (sameSite, secure) to use
* during the eTLD+1 probe. These should match the attributes that will be used
* when setting the actual cookie, so the probe accurately reflects whether a
* domain-scoped cookie can be set in the current context.
+ * `@returns` The resolved eTLD+1 domain to use for setting cookies.+ * `@throws` If the cookie handler throws while probing domains.+ * `@example`+ * getCookieDomain('app.example.com', undefined, { sameSite: 'None', secure: true });
*/
export function getCookieDomain(
hostname = window.location.hostname,
cookieHandler = eTLDCookie,
cookieAttributes?: { sameSite?: string; secure?: boolean },
-) {+): string {
📝 Committable suggestion
‼️IMPORTANT

Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change

/**
* @paramhostname-ThehostnametodeterminetheeTLD+1for.
* @paramcookieHandler-ThecookiehandlertousefortheeTLD+1probe.
* @paramcookieAttributes-Optionalcookieattributes(sameSite,secure)touse
*duringtheeTLD+1probe.Theseshouldmatchtheattributesthatwillbeused
*whensettingtheactualcookie,sotheprobeaccuratelyreflectswhethera
*domain-scopedcookiecanbesetinthecurrentcontext.
*/
exportfunctiongetCookieDomain(
hostname=window.location.hostname,
cookieHandler=eTLDCookie,
 cookieAttributes?: {sameSite?: string; secure?: boolean},
){
/**
*`@param`hostname-ThehostnametodeterminetheeTLD+1for.
*`@param`cookieHandler-ThecookiehandlertousefortheeTLD+1probe.
*`@param`cookieAttributes-Optionalcookieattributes(sameSite,secure)touse
*duringtheeTLD+1probe.Theseshouldmatchtheattributesthatwillbeused
*whensettingtheactualcookie,sotheprobeaccuratelyreflectswhethera
*domain-scopedcookiecanbesetinthecurrentcontext.
*`@returns`TheresolvedeTLD+1domaintouseforsettingcookies.
*`@throws`Ifthecookiehandlerthrowswhileprobingdomains.
*`@example`
*getCookieDomain('app.example.com',undefined,{sameSite: 'None',secure: true});
*/
exportfunctiongetCookieDomain(
hostname=window.location.hostname,
cookieHandler=eTLDCookie,
 cookieAttributes?: {sameSite?: string; secure?: boolean},
): string {
🤖 Prompt for AI Agents
Verify each finding against the current code and only fix it if needed.
In `@packages/clerk-js/src/core/auth/getCookieDomain.ts` around lines 11 - 23, The
exported function getCookieDomain lacks an explicit TypeScript return type and
its JSDoc is incomplete; update the declaration of getCookieDomain to include an
explicit return type (e.g., string | undefined) and ensure cookieAttributes has
precise types (sameSite?: 'Lax' | 'Strict' | 'None' | string; secure?: boolean),
then expand the JSDoc for getCookieDomain to include `@returns` describing the
returned eTLD+1 or undefined, `@throws` describing any errors thrown during the
eTLD+1 probe (e.g., when cookie handling fails), and an `@example` showing typical
usage; reference the function name getCookieDomain and the cookieAttributes
param as the places to change.

 // only compute it once per session to avoid unnecessary cookie ops
 if (cachedETLDPlusOne) {
 return cachedETLDPlusOne;
Expand All@@ -28,17 +40,22 @@ export function getCookieDomain(hostname = window.location.hostname, cookieHandl
 // we know for sure that the first entry is definitely a TLD, skip it
 for (let i = hostnameParts.length - 2; i >= 0; i--) {
 const eTLD = hostnameParts.slice(i).join('.');
 cookieHandler.set('1', { domain: eTLD });
 cookieHandler.set('1', { ...cookieAttributes, domain: eTLD });

 const res = cookieHandler.get();
 if (res === '1') {
 cookieHandler.remove({ domain: eTLD });
 cookieHandler.remove({ ...cookieAttributes, domain: eTLD });
 cachedETLDPlusOne = eTLD;
 return eTLD;
 }

 cookieHandler.remove({ domain: eTLD });
 cookieHandler.remove({ ...cookieAttributes, domain: eTLD });
 }

 return;
 // Fallback to hostname to ensure domain-scoped cookie rather than host-only.
 // In restricted contexts (e.g. cross-origin iframes), the set() will silently
 // fail — which is preferable to creating a host-only cookie that conflicts
 // with domain-scoped cookies set by non-iframe contexts.
 cachedETLDPlusOne = hostname;
@jacekradkojacekradkoFeb 18, 2026

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The reason will be displayed to describe this comment to others. Learn more.

Hmm. I think it makes sense, but I wonder if this could potentially set a cookie on a different subdomain that would still create 2 separate cookies in some cases. 🤔
 return hostname;
}

45 changes: 43 additions & 2 deletions
pnpm-lock.yaml

View file


Open in desktop


Some generated files are not rendered by default. Learn more about how customized files appear on GitHub.


, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

Skip to content
fix(clerk-js): Prevent duplicate __client_uat cookies in iframe contexts#7875

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Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

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 Merged

brkalow
merged 4 commits into

from

Feb 18, 2026
 Merged


fix(clerk-js): Prevent duplicate __client_uat cookies in iframe contexts
#7875
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306e463

fix(clerk-js): Prevent duplicate __client_uat cookies in iframe contexts


brkalow Feb 18, 2026
e4b2d6f

Apply suggestion from @brkalow


brkalow Feb 18, 2026
dc611ff

fix(clerk-js): Pass SameSite/Secure attributes to eTLD+1 cookie probe


brkalow Feb 18, 2026
b245c99

dedupe


brkalow Feb 18, 2026

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5 changes: 5 additions & 0 deletions
.changeset/fix-iframe-client-uat-cookie-domain.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
---
'@clerk/clerk-js': patch
---

Fix `__client_uat` cookie being set on two different domain scopes when app is loaded in both iframe and non-iframe contexts. `getCookieDomain()` now falls back to `hostname` instead of `undefined` when the eTLD+1 probe fails, and the eTLD+1 probe uses the same `SameSite`/`Secure` attributes as the actual cookie to ensure consistent behavior across contexts.

17 changes: 15 additions & 2 deletions
packages/clerk-js/src/core/auth/__tests__/getCookieDomain.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -35,6 +35,19 @@ describe('getCookieDomain', () => {
 expect(result).toBe(hostname);
 });

 it('passes cookie attributes to the probe', () => {
 const hostname = 'app.example.com';
 const handler: CookieHandler = {
 get: vi.fn().mockReturnValueOnce(undefined).mockReturnValueOnce('1'),
 set: vi.fn().mockReturnValue(undefined),
 remove: vi.fn().mockReturnValue(undefined),
 };
 const attrs = { sameSite: 'None', secure: true };
 getCookieDomain(hostname, handler, attrs);
 expect(handler.set).toHaveBeenCalledWith('1', { sameSite: 'None', secure: true, domain: 'example.com' });
 expect(handler.set).toHaveBeenCalledWith('1', { sameSite: 'None', secure: true, domain: 'app.example.com' });
 });

 it('handles localhost', () => {
 const hostname = 'localhost';
 const result = getCookieDomain(hostname);
Expand All@@ -53,15 +66,15 @@ describe('getCookieDomain', () => {
 expect(getCookieDomain('bryce-local')).toBe('bryce-local');
 });

 it('returns undefined if the domain could not be determined', () => {
 it('falls back to hostname if the domain could not be determined', () => {
 const handler: CookieHandler = {
 get: vi.fn().mockReturnValue(undefined),
 set: vi.fn().mockReturnValue(undefined),
 remove: vi.fn().mockReturnValue(undefined),
 };
 const hostname = 'app.hello.co.uk';
 const result = getCookieDomain(hostname, handler);
 expect(result).toBeUndefined();
 expect(result).toBe(hostname);
 });

 it('uses cached value if there is one', () => {
Expand Down

2 changes: 1 addition & 1 deletion
packages/clerk-js/src/core/auth/cookies/clientUat.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -45,7 +45,7 @@ export const createClientUatCookie = (cookieSuffix: string): ClientUatCookieHand
 : 'Strict';
 const secure = getSecureAttribute(sameSite);
 const partitioned = __BUILD_VARIANT_CHIPS__ && secure;
 const domain = getCookieDomain();
 const domain = getCookieDomain(undefined, undefined, { sameSite, secure });

 // '0' indicates the user is signed out
 let val = '0';
Expand Down

27 changes: 22 additions & 5 deletions
packages/clerk-js/src/core/auth/getCookieDomain.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -8,7 +8,19 @@ import { createCookieHandler } from '@clerk/shared/cookie';
let cachedETLDPlusOne: string;
const eTLDCookie = createCookieHandler('__clerk_test_etld');

export function getCookieDomain(hostname = window.location.hostname, cookieHandler = eTLDCookie) {
/**
 * @param hostname - The hostname to determine the eTLD+1 for.
 * @param cookieHandler - The cookie handler to use for the eTLD+1 probe.
 * @param cookieAttributes - Optional cookie attributes (sameSite, secure) to use
 * during the eTLD+1 probe. These should match the attributes that will be used
 * when setting the actual cookie, so the probe accurately reflects whether a
 * domain-scoped cookie can be set in the current context.
 */
export function getCookieDomain(
 hostname = window.location.hostname,
 cookieHandler = eTLDCookie,
 cookieAttributes?: { sameSite?: string; secure?: boolean },
) {

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⚠️ Potential issue | 🟠 Major
🧩 Analysis chain
🏁 Script executed:
cat -n packages/clerk-js/src/core/auth/getCookieDomain.ts
Repository: clerk/javascript
Length of output: 2746
Add explicit return type and complete JSDoc documentation for the exported getCookieDomain function.
This public API lacks an explicit return type annotation. Its JSDoc documentation is also incomplete, missing @returns, @throws, and @example tags required by the TypeScript and JSDoc guidelines.
Suggested patch
 /**
* `@param` hostname - The hostname to determine the eTLD+1 for.
* `@param` cookieHandler - The cookie handler to use for the eTLD+1 probe.
* `@param` cookieAttributes - Optional cookie attributes (sameSite, secure) to use
* during the eTLD+1 probe. These should match the attributes that will be used
* when setting the actual cookie, so the probe accurately reflects whether a
* domain-scoped cookie can be set in the current context.
+ * `@returns` The resolved eTLD+1 domain to use for setting cookies.+ * `@throws` If the cookie handler throws while probing domains.+ * `@example`+ * getCookieDomain('app.example.com', undefined, { sameSite: 'None', secure: true });
*/
export function getCookieDomain(
hostname = window.location.hostname,
cookieHandler = eTLDCookie,
cookieAttributes?: { sameSite?: string; secure?: boolean },
-) {+): string {
📝 Committable suggestion
‼️IMPORTANT

Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change

/**
* @paramhostname-ThehostnametodeterminetheeTLD+1for.
* @paramcookieHandler-ThecookiehandlertousefortheeTLD+1probe.
* @paramcookieAttributes-Optionalcookieattributes(sameSite,secure)touse
*duringtheeTLD+1probe.Theseshouldmatchtheattributesthatwillbeused
*whensettingtheactualcookie,sotheprobeaccuratelyreflectswhethera
*domain-scopedcookiecanbesetinthecurrentcontext.
*/
exportfunctiongetCookieDomain(
hostname=window.location.hostname,
cookieHandler=eTLDCookie,
 cookieAttributes?: {sameSite?: string; secure?: boolean},
){
/**
*`@param`hostname-ThehostnametodeterminetheeTLD+1for.
*`@param`cookieHandler-ThecookiehandlertousefortheeTLD+1probe.
*`@param`cookieAttributes-Optionalcookieattributes(sameSite,secure)touse
*duringtheeTLD+1probe.Theseshouldmatchtheattributesthatwillbeused
*whensettingtheactualcookie,sotheprobeaccuratelyreflectswhethera
*domain-scopedcookiecanbesetinthecurrentcontext.
*`@returns`TheresolvedeTLD+1domaintouseforsettingcookies.
*`@throws`Ifthecookiehandlerthrowswhileprobingdomains.
*`@example`
*getCookieDomain('app.example.com',undefined,{sameSite: 'None',secure: true});
*/
exportfunctiongetCookieDomain(
hostname=window.location.hostname,
cookieHandler=eTLDCookie,
 cookieAttributes?: {sameSite?: string; secure?: boolean},
): string {
🤖 Prompt for AI Agents
Verify each finding against the current code and only fix it if needed.
In `@packages/clerk-js/src/core/auth/getCookieDomain.ts` around lines 11 - 23, The
exported function getCookieDomain lacks an explicit TypeScript return type and
its JSDoc is incomplete; update the declaration of getCookieDomain to include an
explicit return type (e.g., string | undefined) and ensure cookieAttributes has
precise types (sameSite?: 'Lax' | 'Strict' | 'None' | string; secure?: boolean),
then expand the JSDoc for getCookieDomain to include `@returns` describing the
returned eTLD+1 or undefined, `@throws` describing any errors thrown during the
eTLD+1 probe (e.g., when cookie handling fails), and an `@example` showing typical
usage; reference the function name getCookieDomain and the cookieAttributes
param as the places to change.

 // only compute it once per session to avoid unnecessary cookie ops
 if (cachedETLDPlusOne) {
 return cachedETLDPlusOne;
Expand All@@ -28,17 +40,22 @@ export function getCookieDomain(hostname = window.location.hostname, cookieHandl
 // we know for sure that the first entry is definitely a TLD, skip it
 for (let i = hostnameParts.length - 2; i >= 0; i--) {
 const eTLD = hostnameParts.slice(i).join('.');
 cookieHandler.set('1', { domain: eTLD });
 cookieHandler.set('1', { ...cookieAttributes, domain: eTLD });

 const res = cookieHandler.get();
 if (res === '1') {
 cookieHandler.remove({ domain: eTLD });
 cookieHandler.remove({ ...cookieAttributes, domain: eTLD });
 cachedETLDPlusOne = eTLD;
 return eTLD;
 }

 cookieHandler.remove({ domain: eTLD });
 cookieHandler.remove({ ...cookieAttributes, domain: eTLD });
 }

 return;
 // Fallback to hostname to ensure domain-scoped cookie rather than host-only.
 // In restricted contexts (e.g. cross-origin iframes), the set() will silently
 // fail — which is preferable to creating a host-only cookie that conflicts
 // with domain-scoped cookies set by non-iframe contexts.
 cachedETLDPlusOne = hostname;
@jacekradkojacekradkoFeb 18, 2026

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Hmm. I think it makes sense, but I wonder if this could potentially set a cookie on a different subdomain that would still create 2 separate cookies in some cases. 🤔
 return hostname;
}

45 changes: 43 additions & 2 deletions
pnpm-lock.yaml

View file


Open in desktop


Some generated files are not rendered by default. Learn more about how customized files appear on GitHub.


, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default");
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
fix(clerk-js): Prevent duplicate __client_uat cookies in iframe contexts#7875

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to your account

 Merged

brkalow
merged 4 commits into

from

Feb 18, 2026
 Merged


fix(clerk-js): Prevent duplicate __client_uat cookies in iframe contexts
#7875
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306e463

fix(clerk-js): Prevent duplicate __client_uat cookies in iframe contexts


brkalow Feb 18, 2026
e4b2d6f

Apply suggestion from @brkalow


brkalow Feb 18, 2026
dc611ff

fix(clerk-js): Pass SameSite/Secure attributes to eTLD+1 cookie probe


brkalow Feb 18, 2026
b245c99

dedupe


brkalow Feb 18, 2026

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5 changes: 5 additions & 0 deletions
.changeset/fix-iframe-client-uat-cookie-domain.md

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
---
'@clerk/clerk-js': patch
---

Fix `__client_uat` cookie being set on two different domain scopes when app is loaded in both iframe and non-iframe contexts. `getCookieDomain()` now falls back to `hostname` instead of `undefined` when the eTLD+1 probe fails, and the eTLD+1 probe uses the same `SameSite`/`Secure` attributes as the actual cookie to ensure consistent behavior across contexts.

17 changes: 15 additions & 2 deletions
packages/clerk-js/src/core/auth/__tests__/getCookieDomain.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -35,6 +35,19 @@ describe('getCookieDomain', () => {
 expect(result).toBe(hostname);
 });

 it('passes cookie attributes to the probe', () => {
 const hostname = 'app.example.com';
 const handler: CookieHandler = {
 get: vi.fn().mockReturnValueOnce(undefined).mockReturnValueOnce('1'),
 set: vi.fn().mockReturnValue(undefined),
 remove: vi.fn().mockReturnValue(undefined),
 };
 const attrs = { sameSite: 'None', secure: true };
 getCookieDomain(hostname, handler, attrs);
 expect(handler.set).toHaveBeenCalledWith('1', { sameSite: 'None', secure: true, domain: 'example.com' });
 expect(handler.set).toHaveBeenCalledWith('1', { sameSite: 'None', secure: true, domain: 'app.example.com' });
 });

 it('handles localhost', () => {
 const hostname = 'localhost';
 const result = getCookieDomain(hostname);
Expand All@@ -53,15 +66,15 @@ describe('getCookieDomain', () => {
 expect(getCookieDomain('bryce-local')).toBe('bryce-local');
 });

 it('returns undefined if the domain could not be determined', () => {
 it('falls back to hostname if the domain could not be determined', () => {
 const handler: CookieHandler = {
 get: vi.fn().mockReturnValue(undefined),
 set: vi.fn().mockReturnValue(undefined),
 remove: vi.fn().mockReturnValue(undefined),
 };
 const hostname = 'app.hello.co.uk';
 const result = getCookieDomain(hostname, handler);
 expect(result).toBeUndefined();
 expect(result).toBe(hostname);
 });

 it('uses cached value if there is one', () => {
Expand Down

2 changes: 1 addition & 1 deletion
packages/clerk-js/src/core/auth/cookies/clientUat.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -45,7 +45,7 @@ export const createClientUatCookie = (cookieSuffix: string): ClientUatCookieHand
 : 'Strict';
 const secure = getSecureAttribute(sameSite);
 const partitioned = __BUILD_VARIANT_CHIPS__ && secure;
 const domain = getCookieDomain();
 const domain = getCookieDomain(undefined, undefined, { sameSite, secure });

 // '0' indicates the user is signed out
 let val = '0';
Expand Down

27 changes: 22 additions & 5 deletions
packages/clerk-js/src/core/auth/getCookieDomain.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -8,7 +8,19 @@ import { createCookieHandler } from '@clerk/shared/cookie';
let cachedETLDPlusOne: string;
const eTLDCookie = createCookieHandler('__clerk_test_etld');

export function getCookieDomain(hostname = window.location.hostname, cookieHandler = eTLDCookie) {
/**
 * @param hostname - The hostname to determine the eTLD+1 for.
 * @param cookieHandler - The cookie handler to use for the eTLD+1 probe.
 * @param cookieAttributes - Optional cookie attributes (sameSite, secure) to use
 * during the eTLD+1 probe. These should match the attributes that will be used
 * when setting the actual cookie, so the probe accurately reflects whether a
 * domain-scoped cookie can be set in the current context.
 */
export function getCookieDomain(
 hostname = window.location.hostname,
 cookieHandler = eTLDCookie,
 cookieAttributes?: { sameSite?: string; secure?: boolean },
) {

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⚠️ Potential issue | 🟠 Major
🧩 Analysis chain
🏁 Script executed:
cat -n packages/clerk-js/src/core/auth/getCookieDomain.ts
Repository: clerk/javascript
Length of output: 2746
Add explicit return type and complete JSDoc documentation for the exported getCookieDomain function.
This public API lacks an explicit return type annotation. Its JSDoc documentation is also incomplete, missing @returns, @throws, and @example tags required by the TypeScript and JSDoc guidelines.
Suggested patch
 /**
* `@param` hostname - The hostname to determine the eTLD+1 for.
* `@param` cookieHandler - The cookie handler to use for the eTLD+1 probe.
* `@param` cookieAttributes - Optional cookie attributes (sameSite, secure) to use
* during the eTLD+1 probe. These should match the attributes that will be used
* when setting the actual cookie, so the probe accurately reflects whether a
* domain-scoped cookie can be set in the current context.
+ * `@returns` The resolved eTLD+1 domain to use for setting cookies.+ * `@throws` If the cookie handler throws while probing domains.+ * `@example`+ * getCookieDomain('app.example.com', undefined, { sameSite: 'None', secure: true });
*/
export function getCookieDomain(
hostname = window.location.hostname,
cookieHandler = eTLDCookie,
cookieAttributes?: { sameSite?: string; secure?: boolean },
-) {+): string {
📝 Committable suggestion
‼️IMPORTANT

Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change

/**
* @paramhostname-ThehostnametodeterminetheeTLD+1for.
* @paramcookieHandler-ThecookiehandlertousefortheeTLD+1probe.
* @paramcookieAttributes-Optionalcookieattributes(sameSite,secure)touse
*duringtheeTLD+1probe.Theseshouldmatchtheattributesthatwillbeused
*whensettingtheactualcookie,sotheprobeaccuratelyreflectswhethera
*domain-scopedcookiecanbesetinthecurrentcontext.
*/
exportfunctiongetCookieDomain(
hostname=window.location.hostname,
cookieHandler=eTLDCookie,
 cookieAttributes?: {sameSite?: string; secure?: boolean},
){
/**
*`@param`hostname-ThehostnametodeterminetheeTLD+1for.
*`@param`cookieHandler-ThecookiehandlertousefortheeTLD+1probe.
*`@param`cookieAttributes-Optionalcookieattributes(sameSite,secure)touse
*duringtheeTLD+1probe.Theseshouldmatchtheattributesthatwillbeused
*whensettingtheactualcookie,sotheprobeaccuratelyreflectswhethera
*domain-scopedcookiecanbesetinthecurrentcontext.
*`@returns`TheresolvedeTLD+1domaintouseforsettingcookies.
*`@throws`Ifthecookiehandlerthrowswhileprobingdomains.
*`@example`
*getCookieDomain('app.example.com',undefined,{sameSite: 'None',secure: true});
*/
exportfunctiongetCookieDomain(
hostname=window.location.hostname,
cookieHandler=eTLDCookie,
 cookieAttributes?: {sameSite?: string; secure?: boolean},
): string {
🤖 Prompt for AI Agents
Verify each finding against the current code and only fix it if needed.
In `@packages/clerk-js/src/core/auth/getCookieDomain.ts` around lines 11 - 23, The
exported function getCookieDomain lacks an explicit TypeScript return type and
its JSDoc is incomplete; update the declaration of getCookieDomain to include an
explicit return type (e.g., string | undefined) and ensure cookieAttributes has
precise types (sameSite?: 'Lax' | 'Strict' | 'None' | string; secure?: boolean),
then expand the JSDoc for getCookieDomain to include `@returns` describing the
returned eTLD+1 or undefined, `@throws` describing any errors thrown during the
eTLD+1 probe (e.g., when cookie handling fails), and an `@example` showing typical
usage; reference the function name getCookieDomain and the cookieAttributes
param as the places to change.

 // only compute it once per session to avoid unnecessary cookie ops
 if (cachedETLDPlusOne) {
 return cachedETLDPlusOne;
Expand All@@ -28,17 +40,22 @@ export function getCookieDomain(hostname = window.location.hostname, cookieHandl
 // we know for sure that the first entry is definitely a TLD, skip it
 for (let i = hostnameParts.length - 2; i >= 0; i--) {
 const eTLD = hostnameParts.slice(i).join('.');
 cookieHandler.set('1', { domain: eTLD });
 cookieHandler.set('1', { ...cookieAttributes, domain: eTLD });

 const res = cookieHandler.get();
 if (res === '1') {
 cookieHandler.remove({ domain: eTLD });
 cookieHandler.remove({ ...cookieAttributes, domain: eTLD });
 cachedETLDPlusOne = eTLD;
 return eTLD;
 }

 cookieHandler.remove({ domain: eTLD });
 cookieHandler.remove({ ...cookieAttributes, domain: eTLD });
 }

 return;
 // Fallback to hostname to ensure domain-scoped cookie rather than host-only.
 // In restricted contexts (e.g. cross-origin iframes), the set() will silently
 // fail — which is preferable to creating a host-only cookie that conflicts
 // with domain-scoped cookies set by non-iframe contexts.
 cachedETLDPlusOne = hostname;
@jacekradkojacekradkoFeb 18, 2026

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Contributor
Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Hmm. I think it makes sense, but I wonder if this could potentially set a cookie on a different subdomain that would still create 2 separate cookies in some cases. 🤔
 return hostname;
}

45 changes: 43 additions & 2 deletions
pnpm-lock.yaml

View file


Open in desktop


Some generated files are not rendered by default. Learn more about how customized files appear on GitHub.


, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers");
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
fix(clerk-js): Prevent duplicate __client_uat cookies in iframe contexts#7875

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Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

 Sign up for GitHub

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privacy statement. We’ll occasionally send you account related emails.

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 Merged

brkalow
merged 4 commits into

from

Feb 18, 2026
 Merged


fix(clerk-js): Prevent duplicate __client_uat cookies in iframe contexts
#7875
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4 commits


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306e463

fix(clerk-js): Prevent duplicate __client_uat cookies in iframe contexts


brkalow Feb 18, 2026
e4b2d6f

Apply suggestion from @brkalow


brkalow Feb 18, 2026
dc611ff

fix(clerk-js): Pass SameSite/Secure attributes to eTLD+1 cookie probe


brkalow Feb 18, 2026
b245c99

dedupe


brkalow Feb 18, 2026

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5 changes: 5 additions & 0 deletions
.changeset/fix-iframe-client-uat-cookie-domain.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
---
'@clerk/clerk-js': patch
---

Fix `__client_uat` cookie being set on two different domain scopes when app is loaded in both iframe and non-iframe contexts. `getCookieDomain()` now falls back to `hostname` instead of `undefined` when the eTLD+1 probe fails, and the eTLD+1 probe uses the same `SameSite`/`Secure` attributes as the actual cookie to ensure consistent behavior across contexts.

17 changes: 15 additions & 2 deletions
packages/clerk-js/src/core/auth/__tests__/getCookieDomain.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -35,6 +35,19 @@ describe('getCookieDomain', () => {
 expect(result).toBe(hostname);
 });

 it('passes cookie attributes to the probe', () => {
 const hostname = 'app.example.com';
 const handler: CookieHandler = {
 get: vi.fn().mockReturnValueOnce(undefined).mockReturnValueOnce('1'),
 set: vi.fn().mockReturnValue(undefined),
 remove: vi.fn().mockReturnValue(undefined),
 };
 const attrs = { sameSite: 'None', secure: true };
 getCookieDomain(hostname, handler, attrs);
 expect(handler.set).toHaveBeenCalledWith('1', { sameSite: 'None', secure: true, domain: 'example.com' });
 expect(handler.set).toHaveBeenCalledWith('1', { sameSite: 'None', secure: true, domain: 'app.example.com' });
 });

 it('handles localhost', () => {
 const hostname = 'localhost';
 const result = getCookieDomain(hostname);
Expand All@@ -53,15 +66,15 @@ describe('getCookieDomain', () => {
 expect(getCookieDomain('bryce-local')).toBe('bryce-local');
 });

 it('returns undefined if the domain could not be determined', () => {
 it('falls back to hostname if the domain could not be determined', () => {
 const handler: CookieHandler = {
 get: vi.fn().mockReturnValue(undefined),
 set: vi.fn().mockReturnValue(undefined),
 remove: vi.fn().mockReturnValue(undefined),
 };
 const hostname = 'app.hello.co.uk';
 const result = getCookieDomain(hostname, handler);
 expect(result).toBeUndefined();
 expect(result).toBe(hostname);
 });

 it('uses cached value if there is one', () => {
Expand Down

2 changes: 1 addition & 1 deletion
packages/clerk-js/src/core/auth/cookies/clientUat.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -45,7 +45,7 @@ export const createClientUatCookie = (cookieSuffix: string): ClientUatCookieHand
 : 'Strict';
 const secure = getSecureAttribute(sameSite);
 const partitioned = __BUILD_VARIANT_CHIPS__ && secure;
 const domain = getCookieDomain();
 const domain = getCookieDomain(undefined, undefined, { sameSite, secure });

 // '0' indicates the user is signed out
 let val = '0';
Expand Down

27 changes: 22 additions & 5 deletions
packages/clerk-js/src/core/auth/getCookieDomain.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -8,7 +8,19 @@ import { createCookieHandler } from '@clerk/shared/cookie';
let cachedETLDPlusOne: string;
const eTLDCookie = createCookieHandler('__clerk_test_etld');

export function getCookieDomain(hostname = window.location.hostname, cookieHandler = eTLDCookie) {
/**
 * @param hostname - The hostname to determine the eTLD+1 for.
 * @param cookieHandler - The cookie handler to use for the eTLD+1 probe.
 * @param cookieAttributes - Optional cookie attributes (sameSite, secure) to use
 * during the eTLD+1 probe. These should match the attributes that will be used
 * when setting the actual cookie, so the probe accurately reflects whether a
 * domain-scoped cookie can be set in the current context.
 */
export function getCookieDomain(
 hostname = window.location.hostname,
 cookieHandler = eTLDCookie,
 cookieAttributes?: { sameSite?: string; secure?: boolean },
) {

Comment on lines

+11
 to 
+23

@coderabbitaicoderabbitaiBotFeb 18, 2026

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⚠️ Potential issue | 🟠 Major
🧩 Analysis chain
🏁 Script executed:
cat -n packages/clerk-js/src/core/auth/getCookieDomain.ts
Repository: clerk/javascript
Length of output: 2746
Add explicit return type and complete JSDoc documentation for the exported getCookieDomain function.
This public API lacks an explicit return type annotation. Its JSDoc documentation is also incomplete, missing @returns, @throws, and @example tags required by the TypeScript and JSDoc guidelines.
Suggested patch
 /**
* `@param` hostname - The hostname to determine the eTLD+1 for.
* `@param` cookieHandler - The cookie handler to use for the eTLD+1 probe.
* `@param` cookieAttributes - Optional cookie attributes (sameSite, secure) to use
* during the eTLD+1 probe. These should match the attributes that will be used
* when setting the actual cookie, so the probe accurately reflects whether a
* domain-scoped cookie can be set in the current context.
+ * `@returns` The resolved eTLD+1 domain to use for setting cookies.+ * `@throws` If the cookie handler throws while probing domains.+ * `@example`+ * getCookieDomain('app.example.com', undefined, { sameSite: 'None', secure: true });
*/
export function getCookieDomain(
hostname = window.location.hostname,
cookieHandler = eTLDCookie,
cookieAttributes?: { sameSite?: string; secure?: boolean },
-) {+): string {
📝 Committable suggestion
‼️IMPORTANT

Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change

/**
* @paramhostname-ThehostnametodeterminetheeTLD+1for.
* @paramcookieHandler-ThecookiehandlertousefortheeTLD+1probe.
* @paramcookieAttributes-Optionalcookieattributes(sameSite,secure)touse
*duringtheeTLD+1probe.Theseshouldmatchtheattributesthatwillbeused
*whensettingtheactualcookie,sotheprobeaccuratelyreflectswhethera
*domain-scopedcookiecanbesetinthecurrentcontext.
*/
exportfunctiongetCookieDomain(
hostname=window.location.hostname,
cookieHandler=eTLDCookie,
 cookieAttributes?: {sameSite?: string; secure?: boolean},
){
/**
*`@param`hostname-ThehostnametodeterminetheeTLD+1for.
*`@param`cookieHandler-ThecookiehandlertousefortheeTLD+1probe.
*`@param`cookieAttributes-Optionalcookieattributes(sameSite,secure)touse
*duringtheeTLD+1probe.Theseshouldmatchtheattributesthatwillbeused
*whensettingtheactualcookie,sotheprobeaccuratelyreflectswhethera
*domain-scopedcookiecanbesetinthecurrentcontext.
*`@returns`TheresolvedeTLD+1domaintouseforsettingcookies.
*`@throws`Ifthecookiehandlerthrowswhileprobingdomains.
*`@example`
*getCookieDomain('app.example.com',undefined,{sameSite: 'None',secure: true});
*/
exportfunctiongetCookieDomain(
hostname=window.location.hostname,
cookieHandler=eTLDCookie,
 cookieAttributes?: {sameSite?: string; secure?: boolean},
): string {
🤖 Prompt for AI Agents
Verify each finding against the current code and only fix it if needed.
In `@packages/clerk-js/src/core/auth/getCookieDomain.ts` around lines 11 - 23, The
exported function getCookieDomain lacks an explicit TypeScript return type and
its JSDoc is incomplete; update the declaration of getCookieDomain to include an
explicit return type (e.g., string | undefined) and ensure cookieAttributes has
precise types (sameSite?: 'Lax' | 'Strict' | 'None' | string; secure?: boolean),
then expand the JSDoc for getCookieDomain to include `@returns` describing the
returned eTLD+1 or undefined, `@throws` describing any errors thrown during the
eTLD+1 probe (e.g., when cookie handling fails), and an `@example` showing typical
usage; reference the function name getCookieDomain and the cookieAttributes
param as the places to change.

 // only compute it once per session to avoid unnecessary cookie ops
 if (cachedETLDPlusOne) {
 return cachedETLDPlusOne;
Expand All@@ -28,17 +40,22 @@ export function getCookieDomain(hostname = window.location.hostname, cookieHandl
 // we know for sure that the first entry is definitely a TLD, skip it
 for (let i = hostnameParts.length - 2; i >= 0; i--) {
 const eTLD = hostnameParts.slice(i).join('.');
 cookieHandler.set('1', { domain: eTLD });
 cookieHandler.set('1', { ...cookieAttributes, domain: eTLD });

 const res = cookieHandler.get();
 if (res === '1') {
 cookieHandler.remove({ domain: eTLD });
 cookieHandler.remove({ ...cookieAttributes, domain: eTLD });
 cachedETLDPlusOne = eTLD;
 return eTLD;
 }

 cookieHandler.remove({ domain: eTLD });
 cookieHandler.remove({ ...cookieAttributes, domain: eTLD });
 }

 return;
 // Fallback to hostname to ensure domain-scoped cookie rather than host-only.
 // In restricted contexts (e.g. cross-origin iframes), the set() will silently
 // fail — which is preferable to creating a host-only cookie that conflicts
 // with domain-scoped cookies set by non-iframe contexts.
 cachedETLDPlusOne = hostname;
@jacekradkojacekradkoFeb 18, 2026

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Hmm. I think it makes sense, but I wonder if this could potentially set a cookie on a different subdomain that would still create 2 separate cookies in some cases. 🤔
 return hostname;
}

45 changes: 43 additions & 2 deletions
pnpm-lock.yaml

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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

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fix(clerk-js): Prevent duplicate __client_uat cookies in iframe contexts#7875

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 Merged

brkalow
merged 4 commits into

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Feb 18, 2026
 Merged


fix(clerk-js): Prevent duplicate __client_uat cookies in iframe contexts
#7875
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306e463

fix(clerk-js): Prevent duplicate __client_uat cookies in iframe contexts


brkalow Feb 18, 2026
e4b2d6f

Apply suggestion from @brkalow


brkalow Feb 18, 2026
dc611ff

fix(clerk-js): Pass SameSite/Secure attributes to eTLD+1 cookie probe


brkalow Feb 18, 2026
b245c99

dedupe


brkalow Feb 18, 2026

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5 changes: 5 additions & 0 deletions
.changeset/fix-iframe-client-uat-cookie-domain.md

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
---
'@clerk/clerk-js': patch
---

Fix `__client_uat` cookie being set on two different domain scopes when app is loaded in both iframe and non-iframe contexts. `getCookieDomain()` now falls back to `hostname` instead of `undefined` when the eTLD+1 probe fails, and the eTLD+1 probe uses the same `SameSite`/`Secure` attributes as the actual cookie to ensure consistent behavior across contexts.

17 changes: 15 additions & 2 deletions
packages/clerk-js/src/core/auth/__tests__/getCookieDomain.test.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -35,6 +35,19 @@ describe('getCookieDomain', () => {
 expect(result).toBe(hostname);
 });

 it('passes cookie attributes to the probe', () => {
 const hostname = 'app.example.com';
 const handler: CookieHandler = {
 get: vi.fn().mockReturnValueOnce(undefined).mockReturnValueOnce('1'),
 set: vi.fn().mockReturnValue(undefined),
 remove: vi.fn().mockReturnValue(undefined),
 };
 const attrs = { sameSite: 'None', secure: true };
 getCookieDomain(hostname, handler, attrs);
 expect(handler.set).toHaveBeenCalledWith('1', { sameSite: 'None', secure: true, domain: 'example.com' });
 expect(handler.set).toHaveBeenCalledWith('1', { sameSite: 'None', secure: true, domain: 'app.example.com' });
 });

 it('handles localhost', () => {
 const hostname = 'localhost';
 const result = getCookieDomain(hostname);
Expand All@@ -53,15 +66,15 @@ describe('getCookieDomain', () => {
 expect(getCookieDomain('bryce-local')).toBe('bryce-local');
 });

 it('returns undefined if the domain could not be determined', () => {
 it('falls back to hostname if the domain could not be determined', () => {
 const handler: CookieHandler = {
 get: vi.fn().mockReturnValue(undefined),
 set: vi.fn().mockReturnValue(undefined),
 remove: vi.fn().mockReturnValue(undefined),
 };
 const hostname = 'app.hello.co.uk';
 const result = getCookieDomain(hostname, handler);
 expect(result).toBeUndefined();
 expect(result).toBe(hostname);
 });

 it('uses cached value if there is one', () => {
Expand Down

2 changes: 1 addition & 1 deletion
packages/clerk-js/src/core/auth/cookies/clientUat.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -45,7 +45,7 @@ export const createClientUatCookie = (cookieSuffix: string): ClientUatCookieHand
 : 'Strict';
 const secure = getSecureAttribute(sameSite);
 const partitioned = __BUILD_VARIANT_CHIPS__ && secure;
 const domain = getCookieDomain();
 const domain = getCookieDomain(undefined, undefined, { sameSite, secure });

 // '0' indicates the user is signed out
 let val = '0';
Expand Down

27 changes: 22 additions & 5 deletions
packages/clerk-js/src/core/auth/getCookieDomain.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -8,7 +8,19 @@ import { createCookieHandler } from '@clerk/shared/cookie';
let cachedETLDPlusOne: string;
const eTLDCookie = createCookieHandler('__clerk_test_etld');

export function getCookieDomain(hostname = window.location.hostname, cookieHandler = eTLDCookie) {
/**
 * @param hostname - The hostname to determine the eTLD+1 for.
 * @param cookieHandler - The cookie handler to use for the eTLD+1 probe.
 * @param cookieAttributes - Optional cookie attributes (sameSite, secure) to use
 * during the eTLD+1 probe. These should match the attributes that will be used
 * when setting the actual cookie, so the probe accurately reflects whether a
 * domain-scoped cookie can be set in the current context.
 */
export function getCookieDomain(
 hostname = window.location.hostname,
 cookieHandler = eTLDCookie,
 cookieAttributes?: { sameSite?: string; secure?: boolean },
) {

Comment on lines

+11
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+23

@coderabbitaicoderabbitaiBotFeb 18, 2026

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⚠️ Potential issue | 🟠 Major
🧩 Analysis chain
🏁 Script executed:
cat -n packages/clerk-js/src/core/auth/getCookieDomain.ts
Repository: clerk/javascript
Length of output: 2746
Add explicit return type and complete JSDoc documentation for the exported getCookieDomain function.
This public API lacks an explicit return type annotation. Its JSDoc documentation is also incomplete, missing @returns, @throws, and @example tags required by the TypeScript and JSDoc guidelines.
Suggested patch
 /**
* `@param` hostname - The hostname to determine the eTLD+1 for.
* `@param` cookieHandler - The cookie handler to use for the eTLD+1 probe.
* `@param` cookieAttributes - Optional cookie attributes (sameSite, secure) to use
* during the eTLD+1 probe. These should match the attributes that will be used
* when setting the actual cookie, so the probe accurately reflects whether a
* domain-scoped cookie can be set in the current context.
+ * `@returns` The resolved eTLD+1 domain to use for setting cookies.+ * `@throws` If the cookie handler throws while probing domains.+ * `@example`+ * getCookieDomain('app.example.com', undefined, { sameSite: 'None', secure: true });
*/
export function getCookieDomain(
hostname = window.location.hostname,
cookieHandler = eTLDCookie,
cookieAttributes?: { sameSite?: string; secure?: boolean },
-) {+): string {
📝 Committable suggestion
‼️IMPORTANT

Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change

/**
* @paramhostname-ThehostnametodeterminetheeTLD+1for.
* @paramcookieHandler-ThecookiehandlertousefortheeTLD+1probe.
* @paramcookieAttributes-Optionalcookieattributes(sameSite,secure)touse
*duringtheeTLD+1probe.Theseshouldmatchtheattributesthatwillbeused
*whensettingtheactualcookie,sotheprobeaccuratelyreflectswhethera
*domain-scopedcookiecanbesetinthecurrentcontext.
*/
exportfunctiongetCookieDomain(
hostname=window.location.hostname,
cookieHandler=eTLDCookie,
 cookieAttributes?: {sameSite?: string; secure?: boolean},
){
/**
*`@param`hostname-ThehostnametodeterminetheeTLD+1for.
*`@param`cookieHandler-ThecookiehandlertousefortheeTLD+1probe.
*`@param`cookieAttributes-Optionalcookieattributes(sameSite,secure)touse
*duringtheeTLD+1probe.Theseshouldmatchtheattributesthatwillbeused
*whensettingtheactualcookie,sotheprobeaccuratelyreflectswhethera
*domain-scopedcookiecanbesetinthecurrentcontext.
*`@returns`TheresolvedeTLD+1domaintouseforsettingcookies.
*`@throws`Ifthecookiehandlerthrowswhileprobingdomains.
*`@example`
*getCookieDomain('app.example.com',undefined,{sameSite: 'None',secure: true});
*/
exportfunctiongetCookieDomain(
hostname=window.location.hostname,
cookieHandler=eTLDCookie,
 cookieAttributes?: {sameSite?: string; secure?: boolean},
): string {
🤖 Prompt for AI Agents
Verify each finding against the current code and only fix it if needed.
In `@packages/clerk-js/src/core/auth/getCookieDomain.ts` around lines 11 - 23, The
exported function getCookieDomain lacks an explicit TypeScript return type and
its JSDoc is incomplete; update the declaration of getCookieDomain to include an
explicit return type (e.g., string | undefined) and ensure cookieAttributes has
precise types (sameSite?: 'Lax' | 'Strict' | 'None' | string; secure?: boolean),
then expand the JSDoc for getCookieDomain to include `@returns` describing the
returned eTLD+1 or undefined, `@throws` describing any errors thrown during the
eTLD+1 probe (e.g., when cookie handling fails), and an `@example` showing typical
usage; reference the function name getCookieDomain and the cookieAttributes
param as the places to change.

 // only compute it once per session to avoid unnecessary cookie ops
 if (cachedETLDPlusOne) {
 return cachedETLDPlusOne;
Expand All@@ -28,17 +40,22 @@ export function getCookieDomain(hostname = window.location.hostname, cookieHandl
 // we know for sure that the first entry is definitely a TLD, skip it
 for (let i = hostnameParts.length - 2; i >= 0; i--) {
 const eTLD = hostnameParts.slice(i).join('.');
 cookieHandler.set('1', { domain: eTLD });
 cookieHandler.set('1', { ...cookieAttributes, domain: eTLD });

 const res = cookieHandler.get();
 if (res === '1') {
 cookieHandler.remove({ domain: eTLD });
 cookieHandler.remove({ ...cookieAttributes, domain: eTLD });
 cachedETLDPlusOne = eTLD;
 return eTLD;
 }

 cookieHandler.remove({ domain: eTLD });
 cookieHandler.remove({ ...cookieAttributes, domain: eTLD });
 }

 return;
 // Fallback to hostname to ensure domain-scoped cookie rather than host-only.
 // In restricted contexts (e.g. cross-origin iframes), the set() will silently
 // fail — which is preferable to creating a host-only cookie that conflicts
 // with domain-scoped cookies set by non-iframe contexts.
 cachedETLDPlusOne = hostname;
@jacekradkojacekradkoFeb 18, 2026

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Contributor
Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Hmm. I think it makes sense, but I wonder if this could potentially set a cookie on a different subdomain that would still create 2 separate cookies in some cases. 🤔
 return hostname;
}

45 changes: 43 additions & 2 deletions
pnpm-lock.yaml

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