fix(backend): Fix cross-origin handshake bypass#9145

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Merged
dominic-clerk merged 3 commits into from
Jul 18, 2026
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fix(backend): Fix cross-origin handshake bypass #9145

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67c3fdc
fix(backend): Fix cross-origin handshake bypass
dominic-clerk Jul 13, 2026
9bee8e1
Address review comments
dominic-clerk Jul 13, 2026
0cd1824
Merge branch 'main' into dominic/sec-322-cross-origin-handshake-bypas…
wobsoriano Jul 17, 2026
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5 changes: 5 additions & 0 deletions .changeset/khaki-chairs-kiss.md
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Open in desktop
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
---
'@clerk/backend': minor
---

Fix a cross-origin handshake bypass where `isKnownClerkReferrer()` trusted overly broad referrer hosts as Clerk-owned: any `accounts.*` host (e.g. `accounts.attacker.com`), plus dev account-portal domains (`*.accounts.dev` and legacy suffixes) on production instances. These let unrelated origins skip the handshake and its session-freshness check. The referrer is now trusted only for the accounts portal derived from the instance's frontend API, plus dev account-portal domains on non-production instances.
76 changes: 69 additions & 7 deletions packages/backend/src/tokens/__tests__/request.test.ts
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -2085,7 +2085,8 @@ describe('tokens.authenticateRequest(options)', () => {
});
});

test('does not trigger handshake when referer is from production accounts portal', async () => {

@dominic-clerkdominic-clerkJul 13, 2026

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We revert the logic of this test because it tested that example.com's account portal wouldn't trigger a handshake on another (primary.com's) instance.

// accounts.example.com is not this instance's derived accounts portal, so it must not be trusted.
test('triggers handshake when referer is an unrelated accounts.* domain', async () => {
const request = mockRequestWithCookies(
{
referer: 'https://accounts.example.com/sign-in',
Expand All@@ -2107,14 +2108,14 @@ describe('tokens.authenticateRequest(options)', () => {
signInUrl: 'https://primary.com/sign-in',
});

expect(requestState).toBeSignedIn({
expect(requestState).toMatchHandshake({
reason: AuthErrorReason.PrimaryDomainCrossOriginSync,
domain: 'primary.com',
isSatellite: false,
signInUrl: 'https://primary.com/sign-in',
});
});

test('does not trigger handshake when referer is from dev accounts portal (current format)', async () => {
test('does not trigger cross-origin handshake when referer is from dev accounts portal on a dev instance (current format)', async () => {
const request = mockRequestWithCookies(
{
referer: 'https://foo-bar-13.accounts.dev/sign-in',
Expand All@@ -2124,13 +2125,14 @@ describe('tokens.authenticateRequest(options)', () => {
{
__session: mockJwt,
__client_uat: '12345',
__clerk_db_jwt: mockJwt,
},
'https://primary.com/dashboard',
);

const requestState = await authenticateRequest(request, {
...mockOptions(),
publishableKey: PK_LIVE,
publishableKey: PK_TEST,
domain: 'primary.com',
isSatellite: false,
signInUrl: 'https://primary.com/sign-in',
Expand All@@ -2143,7 +2145,7 @@ describe('tokens.authenticateRequest(options)', () => {
});
});

test('does not trigger handshake when referer is from dev accounts portal (legacy format)', async () => {
test('does not trigger cross-origin handshake when referer is from dev accounts portal on a dev instance (legacy format)', async () => {
const request = mockRequestWithCookies(
{
referer: 'https://accounts.foo-bar-13.lcl.dev/sign-in',
Expand All@@ -2153,13 +2155,14 @@ describe('tokens.authenticateRequest(options)', () => {
{
__session: mockJwt,
__client_uat: '12345',
__clerk_db_jwt: mockJwt,
},
'https://primary.com/dashboard',
);

const requestState = await authenticateRequest(request, {
...mockOptions(),
publishableKey: PK_LIVE,
publishableKey: PK_TEST,
domain: 'primary.com',
isSatellite: false,
signInUrl: 'https://primary.com/sign-in',
Expand All@@ -2172,6 +2175,65 @@ describe('tokens.authenticateRequest(options)', () => {
});
});

// A production instance must not trust dev-portal referrers, which are freely obtainable.
test('triggers handshake when referer is a dev accounts portal on a production instance (current format)', async () => {
const request = mockRequestWithCookies(
{
referer: 'https://foo-bar-13.accounts.dev/sign-in',
'sec-fetch-dest': 'document',
'sec-fetch-site': 'cross-site',
},
{
__session: mockJwt,
__client_uat: '12345',
},
'https://primary.com/dashboard',
);

const requestState = await authenticateRequest(request, {
...mockOptions(),
publishableKey: PK_LIVE,
domain: 'primary.com',
isSatellite: false,
signInUrl: 'https://primary.com/sign-in',
});

expect(requestState).toMatchHandshake({
reason: AuthErrorReason.PrimaryDomainCrossOriginSync,
domain: 'primary.com',
signInUrl: 'https://primary.com/sign-in',
});
});

test('triggers handshake when referer is a dev accounts portal on a production instance (legacy format)', async () => {
const request = mockRequestWithCookies(
{
referer: 'https://accounts.foo-bar-13.lcl.dev/sign-in',
'sec-fetch-dest': 'document',
'sec-fetch-site': 'cross-site',
},
{
__session: mockJwt,
__client_uat: '12345',
},
'https://primary.com/dashboard',
);

const requestState = await authenticateRequest(request, {
...mockOptions(),
publishableKey: PK_LIVE,
domain: 'primary.com',
isSatellite: false,
signInUrl: 'https://primary.com/sign-in',
});

expect(requestState).toMatchHandshake({
reason: AuthErrorReason.PrimaryDomainCrossOriginSync,
domain: 'primary.com',
signInUrl: 'https://primary.com/sign-in',
});
});

test('does not trigger cross-origin handshake when referer is from expected accounts portal derived from frontend API', async () => {
const request = mockRequestWithCookies(
{
Expand Down
23 changes: 11 additions & 12 deletions packages/backend/src/tokens/authenticateContext.ts
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -216,11 +216,11 @@ class AuthenticateContext implements AuthenticateContext {
}

/**
* Determines if the referrer URL is from a Clerk domain (accounts portal or FAPI).
* This includes both development and production account portal domains, as well as FAPI domains
* used for redirect-based authentication flows.
* Determines if the referrer URL is from a Clerk domain: the instance's FAPI domain, the accounts
* portal derived from its frontend API, or — on non-production instances only — a development
* account-portal domain.
*
* @returns {boolean} True if the referrer is from a Clerk accounts portal or FAPI domain, false otherwise
* @returns {boolean} True if the referrer is a trusted Clerk domain, false otherwise
*/
public isKnownClerkReferrer(): boolean {
if (!this.referrer) {
Expand All@@ -239,12 +239,16 @@ class AuthenticateContext implements AuthenticateContext {
}
}

// Check for development account portal patterns
if (isLegacyDevAccountPortalOrigin(referrerHost) || isCurrentDevAccountPortalOrigin(referrerHost)) {
// Dev account-portal domains are freely obtainable, so only trust them on non-production instances.
if (
this.instanceType !== 'production' &&
(isLegacyDevAccountPortalOrigin(referrerHost) || isCurrentDevAccountPortalOrigin(referrerHost))
) {
return true;
}

// Check for production account portal by comparing with expected accounts URL
// Only trust the accounts portal derived from this instance's frontend API — never a
// generic `accounts.*` prefix, which any attacker-controlled domain could match.
const expectedAccountsUrl = buildAccountsBaseUrl(this.frontendApi);
if (expectedAccountsUrl) {
const expectedAccountsOrigin = new URL(expectedAccountsUrl).origin;
Expand All@@ -253,11 +257,6 @@ class AuthenticateContext implements AuthenticateContext {
}
}

// Check for generic production accounts patterns (accounts.*)
if (referrerHost.startsWith('accounts.')) {
return true;
}

return false;
} catch {
// Invalid URL format
Expand Down
Loading
, '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" + '

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fix(backend): Fix cross-origin handshake bypass#9145

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 Merged

dominic-clerk
merged 3 commits into

from

Jul 18, 2026
 Merged


fix(backend): Fix cross-origin handshake bypass
#9145
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67c3fdc

fix(backend): Fix cross-origin handshake bypass


dominic-clerk Jul 13, 2026
9bee8e1

Address review comments


dominic-clerk Jul 13, 2026
0cd1824

Merge branch 'main' into dominic/sec-322-cross-origin-handshake-bypas…


wobsoriano Jul 17, 2026

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5 changes: 5 additions & 0 deletions
.changeset/khaki-chairs-kiss.md

View file


Open in desktop

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

Fix a cross-origin handshake bypass where `isKnownClerkReferrer()` trusted overly broad referrer hosts as Clerk-owned: any `accounts.*` host (e.g. `accounts.attacker.com`), plus dev account-portal domains (`*.accounts.dev` and legacy suffixes) on production instances. These let unrelated origins skip the handshake and its session-freshness check. The referrer is now trusted only for the accounts portal derived from the instance's frontend API, plus dev account-portal domains on non-production instances.

76 changes: 69 additions & 7 deletions
packages/backend/src/tokens/__tests__/request.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -2085,7 +2085,8 @@ describe('tokens.authenticateRequest(options)', () => {
 });
 });

 test('does not trigger handshake when referer is from production accounts portal', async () => {
@dominic-clerkdominic-clerkJul 13, 2026

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ContributorAuthor
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We revert the logic of this test because it tested that example.com's account portal wouldn't trigger a handshake on another (primary.com's) instance.
 // accounts.example.com is not this instance's derived accounts portal, so it must not be trusted.
 test('triggers handshake when referer is an unrelated accounts.* domain', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://accounts.example.com/sign-in',
Expand All@@ -2107,14 +2108,14 @@ describe('tokens.authenticateRequest(options)', () => {
 signInUrl: 'https://primary.com/sign-in',
 });

 expect(requestState).toBeSignedIn({
 expect(requestState).toMatchHandshake({
 reason: AuthErrorReason.PrimaryDomainCrossOriginSync,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
 });
 });

 test('does not trigger handshake when referer is from dev accounts portal (current format)', async () => {
 test('does not trigger cross-origin handshake when referer is from dev accounts portal on a dev instance (current format)', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://foo-bar-13.accounts.dev/sign-in',
Expand All@@ -2124,13 +2125,14 @@ describe('tokens.authenticateRequest(options)', () => {
 {
 __session: mockJwt,
 __client_uat: '12345',
 __clerk_db_jwt: mockJwt,
 },
 'https://primary.com/dashboard',
 );

 const requestState = await authenticateRequest(request, {
 ...mockOptions(),
 publishableKey: PK_LIVE,
 publishableKey: PK_TEST,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
Expand All@@ -2143,7 +2145,7 @@ describe('tokens.authenticateRequest(options)', () => {
 });
 });

 test('does not trigger handshake when referer is from dev accounts portal (legacy format)', async () => {
 test('does not trigger cross-origin handshake when referer is from dev accounts portal on a dev instance (legacy format)', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://accounts.foo-bar-13.lcl.dev/sign-in',
Expand All@@ -2153,13 +2155,14 @@ describe('tokens.authenticateRequest(options)', () => {
 {
 __session: mockJwt,
 __client_uat: '12345',
 __clerk_db_jwt: mockJwt,
 },
 'https://primary.com/dashboard',
 );

 const requestState = await authenticateRequest(request, {
 ...mockOptions(),
 publishableKey: PK_LIVE,
 publishableKey: PK_TEST,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
Expand All@@ -2172,6 +2175,65 @@ describe('tokens.authenticateRequest(options)', () => {
 });
 });

 // A production instance must not trust dev-portal referrers, which are freely obtainable.
 test('triggers handshake when referer is a dev accounts portal on a production instance (current format)', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://foo-bar-13.accounts.dev/sign-in',
 'sec-fetch-dest': 'document',
 'sec-fetch-site': 'cross-site',
 },
 {
 __session: mockJwt,
 __client_uat: '12345',
 },
 'https://primary.com/dashboard',
 );

 const requestState = await authenticateRequest(request, {
 ...mockOptions(),
 publishableKey: PK_LIVE,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
 });

 expect(requestState).toMatchHandshake({
 reason: AuthErrorReason.PrimaryDomainCrossOriginSync,
 domain: 'primary.com',
 signInUrl: 'https://primary.com/sign-in',
 });
 });

 test('triggers handshake when referer is a dev accounts portal on a production instance (legacy format)', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://accounts.foo-bar-13.lcl.dev/sign-in',
 'sec-fetch-dest': 'document',
 'sec-fetch-site': 'cross-site',
 },
 {
 __session: mockJwt,
 __client_uat: '12345',
 },
 'https://primary.com/dashboard',
 );

 const requestState = await authenticateRequest(request, {
 ...mockOptions(),
 publishableKey: PK_LIVE,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
 });

 expect(requestState).toMatchHandshake({
 reason: AuthErrorReason.PrimaryDomainCrossOriginSync,
 domain: 'primary.com',
 signInUrl: 'https://primary.com/sign-in',
 });
 });

 test('does not trigger cross-origin handshake when referer is from expected accounts portal derived from frontend API', async () => {
 const request = mockRequestWithCookies(
 {
Expand Down

23 changes: 11 additions & 12 deletions
packages/backend/src/tokens/authenticateContext.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -216,11 +216,11 @@ class AuthenticateContext implements AuthenticateContext {
 }

 /**
 * Determines if the referrer URL is from a Clerk domain (accounts portal or FAPI).
 * This includes both development and production account portal domains, as well as FAPI domains
 * used for redirect-based authentication flows.
 * Determines if the referrer URL is from a Clerk domain: the instance's FAPI domain, the accounts
 * portal derived from its frontend API, or — on non-production instances only — a development
 * account-portal domain.
 *
 * @returns {boolean} True if the referrer is from a Clerk accounts portal or FAPI domain, false otherwise
 * @returns {boolean} True if the referrer is a trusted Clerk domain, false otherwise
 */
 public isKnownClerkReferrer(): boolean {
 if (!this.referrer) {
Expand All@@ -239,12 +239,16 @@ class AuthenticateContext implements AuthenticateContext {
 }
 }

 // Check for development account portal patterns
 if (isLegacyDevAccountPortalOrigin(referrerHost) || isCurrentDevAccountPortalOrigin(referrerHost)) {
 // Dev account-portal domains are freely obtainable, so only trust them on non-production instances.
 if (
 this.instanceType !== 'production' &&
 (isLegacyDevAccountPortalOrigin(referrerHost) || isCurrentDevAccountPortalOrigin(referrerHost))
 ) {
 return true;
 }

 // Check for production account portal by comparing with expected accounts URL
 // Only trust the accounts portal derived from this instance's frontend API — never a
 // generic `accounts.*` prefix, which any attacker-controlled domain could match.
 const expectedAccountsUrl = buildAccountsBaseUrl(this.frontendApi);
 if (expectedAccountsUrl) {
 const expectedAccountsOrigin = new URL(expectedAccountsUrl).origin;
Expand All@@ -253,11 +257,6 @@ class AuthenticateContext implements AuthenticateContext {
 }
 }

 // Check for generic production accounts patterns (accounts.*)
 if (referrerHost.startsWith('accounts.')) {
 return true;
 }

 return false;
 } catch {
 // Invalid URL format
Expand Down
Loading

, '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('^' + ".*" + '

Skip to content
fix(backend): Fix cross-origin handshake bypass#9145

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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

dominic-clerk
merged 3 commits into

from

Jul 18, 2026
 Merged


fix(backend): Fix cross-origin handshake bypass
#9145
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67c3fdc

fix(backend): Fix cross-origin handshake bypass


dominic-clerk Jul 13, 2026
9bee8e1

Address review comments


dominic-clerk Jul 13, 2026
0cd1824

Merge branch 'main' into dominic/sec-322-cross-origin-handshake-bypas…


wobsoriano Jul 17, 2026

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5 changes: 5 additions & 0 deletions
.changeset/khaki-chairs-kiss.md

View file


Open in desktop

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

Fix a cross-origin handshake bypass where `isKnownClerkReferrer()` trusted overly broad referrer hosts as Clerk-owned: any `accounts.*` host (e.g. `accounts.attacker.com`), plus dev account-portal domains (`*.accounts.dev` and legacy suffixes) on production instances. These let unrelated origins skip the handshake and its session-freshness check. The referrer is now trusted only for the accounts portal derived from the instance's frontend API, plus dev account-portal domains on non-production instances.

76 changes: 69 additions & 7 deletions
packages/backend/src/tokens/__tests__/request.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -2085,7 +2085,8 @@ describe('tokens.authenticateRequest(options)', () => {
 });
 });

 test('does not trigger handshake when referer is from production accounts portal', async () => {
@dominic-clerkdominic-clerkJul 13, 2026

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ContributorAuthor
Choose a reason for hiding this comment

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

We revert the logic of this test because it tested that example.com's account portal wouldn't trigger a handshake on another (primary.com's) instance.
 // accounts.example.com is not this instance's derived accounts portal, so it must not be trusted.
 test('triggers handshake when referer is an unrelated accounts.* domain', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://accounts.example.com/sign-in',
Expand All@@ -2107,14 +2108,14 @@ describe('tokens.authenticateRequest(options)', () => {
 signInUrl: 'https://primary.com/sign-in',
 });

 expect(requestState).toBeSignedIn({
 expect(requestState).toMatchHandshake({
 reason: AuthErrorReason.PrimaryDomainCrossOriginSync,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
 });
 });

 test('does not trigger handshake when referer is from dev accounts portal (current format)', async () => {
 test('does not trigger cross-origin handshake when referer is from dev accounts portal on a dev instance (current format)', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://foo-bar-13.accounts.dev/sign-in',
Expand All@@ -2124,13 +2125,14 @@ describe('tokens.authenticateRequest(options)', () => {
 {
 __session: mockJwt,
 __client_uat: '12345',
 __clerk_db_jwt: mockJwt,
 },
 'https://primary.com/dashboard',
 );

 const requestState = await authenticateRequest(request, {
 ...mockOptions(),
 publishableKey: PK_LIVE,
 publishableKey: PK_TEST,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
Expand All@@ -2143,7 +2145,7 @@ describe('tokens.authenticateRequest(options)', () => {
 });
 });

 test('does not trigger handshake when referer is from dev accounts portal (legacy format)', async () => {
 test('does not trigger cross-origin handshake when referer is from dev accounts portal on a dev instance (legacy format)', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://accounts.foo-bar-13.lcl.dev/sign-in',
Expand All@@ -2153,13 +2155,14 @@ describe('tokens.authenticateRequest(options)', () => {
 {
 __session: mockJwt,
 __client_uat: '12345',
 __clerk_db_jwt: mockJwt,
 },
 'https://primary.com/dashboard',
 );

 const requestState = await authenticateRequest(request, {
 ...mockOptions(),
 publishableKey: PK_LIVE,
 publishableKey: PK_TEST,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
Expand All@@ -2172,6 +2175,65 @@ describe('tokens.authenticateRequest(options)', () => {
 });
 });

 // A production instance must not trust dev-portal referrers, which are freely obtainable.
 test('triggers handshake when referer is a dev accounts portal on a production instance (current format)', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://foo-bar-13.accounts.dev/sign-in',
 'sec-fetch-dest': 'document',
 'sec-fetch-site': 'cross-site',
 },
 {
 __session: mockJwt,
 __client_uat: '12345',
 },
 'https://primary.com/dashboard',
 );

 const requestState = await authenticateRequest(request, {
 ...mockOptions(),
 publishableKey: PK_LIVE,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
 });

 expect(requestState).toMatchHandshake({
 reason: AuthErrorReason.PrimaryDomainCrossOriginSync,
 domain: 'primary.com',
 signInUrl: 'https://primary.com/sign-in',
 });
 });

 test('triggers handshake when referer is a dev accounts portal on a production instance (legacy format)', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://accounts.foo-bar-13.lcl.dev/sign-in',
 'sec-fetch-dest': 'document',
 'sec-fetch-site': 'cross-site',
 },
 {
 __session: mockJwt,
 __client_uat: '12345',
 },
 'https://primary.com/dashboard',
 );

 const requestState = await authenticateRequest(request, {
 ...mockOptions(),
 publishableKey: PK_LIVE,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
 });

 expect(requestState).toMatchHandshake({
 reason: AuthErrorReason.PrimaryDomainCrossOriginSync,
 domain: 'primary.com',
 signInUrl: 'https://primary.com/sign-in',
 });
 });

 test('does not trigger cross-origin handshake when referer is from expected accounts portal derived from frontend API', async () => {
 const request = mockRequestWithCookies(
 {
Expand Down

23 changes: 11 additions & 12 deletions
packages/backend/src/tokens/authenticateContext.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -216,11 +216,11 @@ class AuthenticateContext implements AuthenticateContext {
 }

 /**
 * Determines if the referrer URL is from a Clerk domain (accounts portal or FAPI).
 * This includes both development and production account portal domains, as well as FAPI domains
 * used for redirect-based authentication flows.
 * Determines if the referrer URL is from a Clerk domain: the instance's FAPI domain, the accounts
 * portal derived from its frontend API, or — on non-production instances only — a development
 * account-portal domain.
 *
 * @returns {boolean} True if the referrer is from a Clerk accounts portal or FAPI domain, false otherwise
 * @returns {boolean} True if the referrer is a trusted Clerk domain, false otherwise
 */
 public isKnownClerkReferrer(): boolean {
 if (!this.referrer) {
Expand All@@ -239,12 +239,16 @@ class AuthenticateContext implements AuthenticateContext {
 }
 }

 // Check for development account portal patterns
 if (isLegacyDevAccountPortalOrigin(referrerHost) || isCurrentDevAccountPortalOrigin(referrerHost)) {
 // Dev account-portal domains are freely obtainable, so only trust them on non-production instances.
 if (
 this.instanceType !== 'production' &&
 (isLegacyDevAccountPortalOrigin(referrerHost) || isCurrentDevAccountPortalOrigin(referrerHost))
 ) {
 return true;
 }

 // Check for production account portal by comparing with expected accounts URL
 // Only trust the accounts portal derived from this instance's frontend API — never a
 // generic `accounts.*` prefix, which any attacker-controlled domain could match.
 const expectedAccountsUrl = buildAccountsBaseUrl(this.frontendApi);
 if (expectedAccountsUrl) {
 const expectedAccountsOrigin = new URL(expectedAccountsUrl).origin;
Expand All@@ -253,11 +257,6 @@ class AuthenticateContext implements AuthenticateContext {
 }
 }

 // Check for generic production accounts patterns (accounts.*)
 if (referrerHost.startsWith('accounts.')) {
 return true;
 }

 return false;
 } catch {
 // Invalid URL format
Expand Down
Loading

, '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('^' + ".*" + '

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fix(backend): Fix cross-origin handshake bypass#9145

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dominic-clerk
merged 3 commits into

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Jul 18, 2026
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fix(backend): Fix cross-origin handshake bypass
#9145
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67c3fdc

fix(backend): Fix cross-origin handshake bypass


dominic-clerk Jul 13, 2026
9bee8e1

Address review comments


dominic-clerk Jul 13, 2026
0cd1824

Merge branch 'main' into dominic/sec-322-cross-origin-handshake-bypas…


wobsoriano Jul 17, 2026

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5 changes: 5 additions & 0 deletions
.changeset/khaki-chairs-kiss.md

View file


Open in desktop

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

Fix a cross-origin handshake bypass where `isKnownClerkReferrer()` trusted overly broad referrer hosts as Clerk-owned: any `accounts.*` host (e.g. `accounts.attacker.com`), plus dev account-portal domains (`*.accounts.dev` and legacy suffixes) on production instances. These let unrelated origins skip the handshake and its session-freshness check. The referrer is now trusted only for the accounts portal derived from the instance's frontend API, plus dev account-portal domains on non-production instances.

76 changes: 69 additions & 7 deletions
packages/backend/src/tokens/__tests__/request.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -2085,7 +2085,8 @@ describe('tokens.authenticateRequest(options)', () => {
 });
 });

 test('does not trigger handshake when referer is from production accounts portal', async () => {
@dominic-clerkdominic-clerkJul 13, 2026

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We revert the logic of this test because it tested that example.com's account portal wouldn't trigger a handshake on another (primary.com's) instance.
 // accounts.example.com is not this instance's derived accounts portal, so it must not be trusted.
 test('triggers handshake when referer is an unrelated accounts.* domain', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://accounts.example.com/sign-in',
Expand All@@ -2107,14 +2108,14 @@ describe('tokens.authenticateRequest(options)', () => {
 signInUrl: 'https://primary.com/sign-in',
 });

 expect(requestState).toBeSignedIn({
 expect(requestState).toMatchHandshake({
 reason: AuthErrorReason.PrimaryDomainCrossOriginSync,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
 });
 });

 test('does not trigger handshake when referer is from dev accounts portal (current format)', async () => {
 test('does not trigger cross-origin handshake when referer is from dev accounts portal on a dev instance (current format)', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://foo-bar-13.accounts.dev/sign-in',
Expand All@@ -2124,13 +2125,14 @@ describe('tokens.authenticateRequest(options)', () => {
 {
 __session: mockJwt,
 __client_uat: '12345',
 __clerk_db_jwt: mockJwt,
 },
 'https://primary.com/dashboard',
 );

 const requestState = await authenticateRequest(request, {
 ...mockOptions(),
 publishableKey: PK_LIVE,
 publishableKey: PK_TEST,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
Expand All@@ -2143,7 +2145,7 @@ describe('tokens.authenticateRequest(options)', () => {
 });
 });

 test('does not trigger handshake when referer is from dev accounts portal (legacy format)', async () => {
 test('does not trigger cross-origin handshake when referer is from dev accounts portal on a dev instance (legacy format)', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://accounts.foo-bar-13.lcl.dev/sign-in',
Expand All@@ -2153,13 +2155,14 @@ describe('tokens.authenticateRequest(options)', () => {
 {
 __session: mockJwt,
 __client_uat: '12345',
 __clerk_db_jwt: mockJwt,
 },
 'https://primary.com/dashboard',
 );

 const requestState = await authenticateRequest(request, {
 ...mockOptions(),
 publishableKey: PK_LIVE,
 publishableKey: PK_TEST,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
Expand All@@ -2172,6 +2175,65 @@ describe('tokens.authenticateRequest(options)', () => {
 });
 });

 // A production instance must not trust dev-portal referrers, which are freely obtainable.
 test('triggers handshake when referer is a dev accounts portal on a production instance (current format)', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://foo-bar-13.accounts.dev/sign-in',
 'sec-fetch-dest': 'document',
 'sec-fetch-site': 'cross-site',
 },
 {
 __session: mockJwt,
 __client_uat: '12345',
 },
 'https://primary.com/dashboard',
 );

 const requestState = await authenticateRequest(request, {
 ...mockOptions(),
 publishableKey: PK_LIVE,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
 });

 expect(requestState).toMatchHandshake({
 reason: AuthErrorReason.PrimaryDomainCrossOriginSync,
 domain: 'primary.com',
 signInUrl: 'https://primary.com/sign-in',
 });
 });

 test('triggers handshake when referer is a dev accounts portal on a production instance (legacy format)', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://accounts.foo-bar-13.lcl.dev/sign-in',
 'sec-fetch-dest': 'document',
 'sec-fetch-site': 'cross-site',
 },
 {
 __session: mockJwt,
 __client_uat: '12345',
 },
 'https://primary.com/dashboard',
 );

 const requestState = await authenticateRequest(request, {
 ...mockOptions(),
 publishableKey: PK_LIVE,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
 });

 expect(requestState).toMatchHandshake({
 reason: AuthErrorReason.PrimaryDomainCrossOriginSync,
 domain: 'primary.com',
 signInUrl: 'https://primary.com/sign-in',
 });
 });

 test('does not trigger cross-origin handshake when referer is from expected accounts portal derived from frontend API', async () => {
 const request = mockRequestWithCookies(
 {
Expand Down

23 changes: 11 additions & 12 deletions
packages/backend/src/tokens/authenticateContext.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -216,11 +216,11 @@ class AuthenticateContext implements AuthenticateContext {
 }

 /**
 * Determines if the referrer URL is from a Clerk domain (accounts portal or FAPI).
 * This includes both development and production account portal domains, as well as FAPI domains
 * used for redirect-based authentication flows.
 * Determines if the referrer URL is from a Clerk domain: the instance's FAPI domain, the accounts
 * portal derived from its frontend API, or — on non-production instances only — a development
 * account-portal domain.
 *
 * @returns {boolean} True if the referrer is from a Clerk accounts portal or FAPI domain, false otherwise
 * @returns {boolean} True if the referrer is a trusted Clerk domain, false otherwise
 */
 public isKnownClerkReferrer(): boolean {
 if (!this.referrer) {
Expand All@@ -239,12 +239,16 @@ class AuthenticateContext implements AuthenticateContext {
 }
 }

 // Check for development account portal patterns
 if (isLegacyDevAccountPortalOrigin(referrerHost) || isCurrentDevAccountPortalOrigin(referrerHost)) {
 // Dev account-portal domains are freely obtainable, so only trust them on non-production instances.
 if (
 this.instanceType !== 'production' &&
 (isLegacyDevAccountPortalOrigin(referrerHost) || isCurrentDevAccountPortalOrigin(referrerHost))
 ) {
 return true;
 }

 // Check for production account portal by comparing with expected accounts URL
 // Only trust the accounts portal derived from this instance's frontend API — never a
 // generic `accounts.*` prefix, which any attacker-controlled domain could match.
 const expectedAccountsUrl = buildAccountsBaseUrl(this.frontendApi);
 if (expectedAccountsUrl) {
 const expectedAccountsOrigin = new URL(expectedAccountsUrl).origin;
Expand All@@ -253,11 +257,6 @@ class AuthenticateContext implements AuthenticateContext {
 }
 }

 // Check for generic production accounts patterns (accounts.*)
 if (referrerHost.startsWith('accounts.')) {
 return true;
 }

 return false;
 } catch {
 // Invalid URL format
Expand Down
Loading

, '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" + '

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fix(backend): Fix cross-origin handshake bypass#9145

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 Merged

dominic-clerk
merged 3 commits into

from

Jul 18, 2026
 Merged


fix(backend): Fix cross-origin handshake bypass
#9145
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67c3fdc

fix(backend): Fix cross-origin handshake bypass


dominic-clerk Jul 13, 2026
9bee8e1

Address review comments


dominic-clerk Jul 13, 2026
0cd1824

Merge branch 'main' into dominic/sec-322-cross-origin-handshake-bypas…


wobsoriano Jul 17, 2026

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5 changes: 5 additions & 0 deletions
.changeset/khaki-chairs-kiss.md

View file


Open in desktop

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

Fix a cross-origin handshake bypass where `isKnownClerkReferrer()` trusted overly broad referrer hosts as Clerk-owned: any `accounts.*` host (e.g. `accounts.attacker.com`), plus dev account-portal domains (`*.accounts.dev` and legacy suffixes) on production instances. These let unrelated origins skip the handshake and its session-freshness check. The referrer is now trusted only for the accounts portal derived from the instance's frontend API, plus dev account-portal domains on non-production instances.

76 changes: 69 additions & 7 deletions
packages/backend/src/tokens/__tests__/request.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -2085,7 +2085,8 @@ describe('tokens.authenticateRequest(options)', () => {
 });
 });

 test('does not trigger handshake when referer is from production accounts portal', async () => {
@dominic-clerkdominic-clerkJul 13, 2026

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ContributorAuthor
Choose a reason for hiding this comment

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

We revert the logic of this test because it tested that example.com's account portal wouldn't trigger a handshake on another (primary.com's) instance.
 // accounts.example.com is not this instance's derived accounts portal, so it must not be trusted.
 test('triggers handshake when referer is an unrelated accounts.* domain', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://accounts.example.com/sign-in',
Expand All@@ -2107,14 +2108,14 @@ describe('tokens.authenticateRequest(options)', () => {
 signInUrl: 'https://primary.com/sign-in',
 });

 expect(requestState).toBeSignedIn({
 expect(requestState).toMatchHandshake({
 reason: AuthErrorReason.PrimaryDomainCrossOriginSync,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
 });
 });

 test('does not trigger handshake when referer is from dev accounts portal (current format)', async () => {
 test('does not trigger cross-origin handshake when referer is from dev accounts portal on a dev instance (current format)', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://foo-bar-13.accounts.dev/sign-in',
Expand All@@ -2124,13 +2125,14 @@ describe('tokens.authenticateRequest(options)', () => {
 {
 __session: mockJwt,
 __client_uat: '12345',
 __clerk_db_jwt: mockJwt,
 },
 'https://primary.com/dashboard',
 );

 const requestState = await authenticateRequest(request, {
 ...mockOptions(),
 publishableKey: PK_LIVE,
 publishableKey: PK_TEST,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
Expand All@@ -2143,7 +2145,7 @@ describe('tokens.authenticateRequest(options)', () => {
 });
 });

 test('does not trigger handshake when referer is from dev accounts portal (legacy format)', async () => {
 test('does not trigger cross-origin handshake when referer is from dev accounts portal on a dev instance (legacy format)', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://accounts.foo-bar-13.lcl.dev/sign-in',
Expand All@@ -2153,13 +2155,14 @@ describe('tokens.authenticateRequest(options)', () => {
 {
 __session: mockJwt,
 __client_uat: '12345',
 __clerk_db_jwt: mockJwt,
 },
 'https://primary.com/dashboard',
 );

 const requestState = await authenticateRequest(request, {
 ...mockOptions(),
 publishableKey: PK_LIVE,
 publishableKey: PK_TEST,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
Expand All@@ -2172,6 +2175,65 @@ describe('tokens.authenticateRequest(options)', () => {
 });
 });

 // A production instance must not trust dev-portal referrers, which are freely obtainable.
 test('triggers handshake when referer is a dev accounts portal on a production instance (current format)', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://foo-bar-13.accounts.dev/sign-in',
 'sec-fetch-dest': 'document',
 'sec-fetch-site': 'cross-site',
 },
 {
 __session: mockJwt,
 __client_uat: '12345',
 },
 'https://primary.com/dashboard',
 );

 const requestState = await authenticateRequest(request, {
 ...mockOptions(),
 publishableKey: PK_LIVE,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
 });

 expect(requestState).toMatchHandshake({
 reason: AuthErrorReason.PrimaryDomainCrossOriginSync,
 domain: 'primary.com',
 signInUrl: 'https://primary.com/sign-in',
 });
 });

 test('triggers handshake when referer is a dev accounts portal on a production instance (legacy format)', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://accounts.foo-bar-13.lcl.dev/sign-in',
 'sec-fetch-dest': 'document',
 'sec-fetch-site': 'cross-site',
 },
 {
 __session: mockJwt,
 __client_uat: '12345',
 },
 'https://primary.com/dashboard',
 );

 const requestState = await authenticateRequest(request, {
 ...mockOptions(),
 publishableKey: PK_LIVE,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
 });

 expect(requestState).toMatchHandshake({
 reason: AuthErrorReason.PrimaryDomainCrossOriginSync,
 domain: 'primary.com',
 signInUrl: 'https://primary.com/sign-in',
 });
 });

 test('does not trigger cross-origin handshake when referer is from expected accounts portal derived from frontend API', async () => {
 const request = mockRequestWithCookies(
 {
Expand Down

23 changes: 11 additions & 12 deletions
packages/backend/src/tokens/authenticateContext.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -216,11 +216,11 @@ class AuthenticateContext implements AuthenticateContext {
 }

 /**
 * Determines if the referrer URL is from a Clerk domain (accounts portal or FAPI).
 * This includes both development and production account portal domains, as well as FAPI domains
 * used for redirect-based authentication flows.
 * Determines if the referrer URL is from a Clerk domain: the instance's FAPI domain, the accounts
 * portal derived from its frontend API, or — on non-production instances only — a development
 * account-portal domain.
 *
 * @returns {boolean} True if the referrer is from a Clerk accounts portal or FAPI domain, false otherwise
 * @returns {boolean} True if the referrer is a trusted Clerk domain, false otherwise
 */
 public isKnownClerkReferrer(): boolean {
 if (!this.referrer) {
Expand All@@ -239,12 +239,16 @@ class AuthenticateContext implements AuthenticateContext {
 }
 }

 // Check for development account portal patterns
 if (isLegacyDevAccountPortalOrigin(referrerHost) || isCurrentDevAccountPortalOrigin(referrerHost)) {
 // Dev account-portal domains are freely obtainable, so only trust them on non-production instances.
 if (
 this.instanceType !== 'production' &&
 (isLegacyDevAccountPortalOrigin(referrerHost) || isCurrentDevAccountPortalOrigin(referrerHost))
 ) {
 return true;
 }

 // Check for production account portal by comparing with expected accounts URL
 // Only trust the accounts portal derived from this instance's frontend API — never a
 // generic `accounts.*` prefix, which any attacker-controlled domain could match.
 const expectedAccountsUrl = buildAccountsBaseUrl(this.frontendApi);
 if (expectedAccountsUrl) {
 const expectedAccountsOrigin = new URL(expectedAccountsUrl).origin;
Expand All@@ -253,11 +257,6 @@ class AuthenticateContext implements AuthenticateContext {
 }
 }

 // Check for generic production accounts patterns (accounts.*)
 if (referrerHost.startsWith('accounts.')) {
 return true;
 }

 return false;
 } catch {
 // Invalid URL format
Expand Down
Loading

, '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(backend): Fix cross-origin handshake bypass#9145

New issue

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

By clicking “Sign up for GitHub”, you agree to our terms of service and
privacy statement. We’ll occasionally send you account related emails.

Already on GitHub?
Sign in
to your account

 Merged

dominic-clerk
merged 3 commits into

from

Jul 18, 2026
 Merged


fix(backend): Fix cross-origin handshake bypass
#9145
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67c3fdc

fix(backend): Fix cross-origin handshake bypass


dominic-clerk Jul 13, 2026
9bee8e1

Address review comments


dominic-clerk Jul 13, 2026
0cd1824

Merge branch 'main' into dominic/sec-322-cross-origin-handshake-bypas…


wobsoriano Jul 17, 2026

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5 changes: 5 additions & 0 deletions
.changeset/khaki-chairs-kiss.md

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Open in desktop

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

Fix a cross-origin handshake bypass where `isKnownClerkReferrer()` trusted overly broad referrer hosts as Clerk-owned: any `accounts.*` host (e.g. `accounts.attacker.com`), plus dev account-portal domains (`*.accounts.dev` and legacy suffixes) on production instances. These let unrelated origins skip the handshake and its session-freshness check. The referrer is now trusted only for the accounts portal derived from the instance's frontend API, plus dev account-portal domains on non-production instances.

76 changes: 69 additions & 7 deletions
packages/backend/src/tokens/__tests__/request.test.ts

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Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -2085,7 +2085,8 @@ describe('tokens.authenticateRequest(options)', () => {
 });
 });

 test('does not trigger handshake when referer is from production accounts portal', async () => {
@dominic-clerkdominic-clerkJul 13, 2026

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We revert the logic of this test because it tested that example.com's account portal wouldn't trigger a handshake on another (primary.com's) instance.
 // accounts.example.com is not this instance's derived accounts portal, so it must not be trusted.
 test('triggers handshake when referer is an unrelated accounts.* domain', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://accounts.example.com/sign-in',
Expand All@@ -2107,14 +2108,14 @@ describe('tokens.authenticateRequest(options)', () => {
 signInUrl: 'https://primary.com/sign-in',
 });

 expect(requestState).toBeSignedIn({
 expect(requestState).toMatchHandshake({
 reason: AuthErrorReason.PrimaryDomainCrossOriginSync,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
 });
 });

 test('does not trigger handshake when referer is from dev accounts portal (current format)', async () => {
 test('does not trigger cross-origin handshake when referer is from dev accounts portal on a dev instance (current format)', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://foo-bar-13.accounts.dev/sign-in',
Expand All@@ -2124,13 +2125,14 @@ describe('tokens.authenticateRequest(options)', () => {
 {
 __session: mockJwt,
 __client_uat: '12345',
 __clerk_db_jwt: mockJwt,
 },
 'https://primary.com/dashboard',
 );

 const requestState = await authenticateRequest(request, {
 ...mockOptions(),
 publishableKey: PK_LIVE,
 publishableKey: PK_TEST,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
Expand All@@ -2143,7 +2145,7 @@ describe('tokens.authenticateRequest(options)', () => {
 });
 });

 test('does not trigger handshake when referer is from dev accounts portal (legacy format)', async () => {
 test('does not trigger cross-origin handshake when referer is from dev accounts portal on a dev instance (legacy format)', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://accounts.foo-bar-13.lcl.dev/sign-in',
Expand All@@ -2153,13 +2155,14 @@ describe('tokens.authenticateRequest(options)', () => {
 {
 __session: mockJwt,
 __client_uat: '12345',
 __clerk_db_jwt: mockJwt,
 },
 'https://primary.com/dashboard',
 );

 const requestState = await authenticateRequest(request, {
 ...mockOptions(),
 publishableKey: PK_LIVE,
 publishableKey: PK_TEST,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
Expand All@@ -2172,6 +2175,65 @@ describe('tokens.authenticateRequest(options)', () => {
 });
 });

 // A production instance must not trust dev-portal referrers, which are freely obtainable.
 test('triggers handshake when referer is a dev accounts portal on a production instance (current format)', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://foo-bar-13.accounts.dev/sign-in',
 'sec-fetch-dest': 'document',
 'sec-fetch-site': 'cross-site',
 },
 {
 __session: mockJwt,
 __client_uat: '12345',
 },
 'https://primary.com/dashboard',
 );

 const requestState = await authenticateRequest(request, {
 ...mockOptions(),
 publishableKey: PK_LIVE,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
 });

 expect(requestState).toMatchHandshake({
 reason: AuthErrorReason.PrimaryDomainCrossOriginSync,
 domain: 'primary.com',
 signInUrl: 'https://primary.com/sign-in',
 });
 });

 test('triggers handshake when referer is a dev accounts portal on a production instance (legacy format)', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://accounts.foo-bar-13.lcl.dev/sign-in',
 'sec-fetch-dest': 'document',
 'sec-fetch-site': 'cross-site',
 },
 {
 __session: mockJwt,
 __client_uat: '12345',
 },
 'https://primary.com/dashboard',
 );

 const requestState = await authenticateRequest(request, {
 ...mockOptions(),
 publishableKey: PK_LIVE,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
 });

 expect(requestState).toMatchHandshake({
 reason: AuthErrorReason.PrimaryDomainCrossOriginSync,
 domain: 'primary.com',
 signInUrl: 'https://primary.com/sign-in',
 });
 });

 test('does not trigger cross-origin handshake when referer is from expected accounts portal derived from frontend API', async () => {
 const request = mockRequestWithCookies(
 {
Expand Down

23 changes: 11 additions & 12 deletions
packages/backend/src/tokens/authenticateContext.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -216,11 +216,11 @@ class AuthenticateContext implements AuthenticateContext {
 }

 /**
 * Determines if the referrer URL is from a Clerk domain (accounts portal or FAPI).
 * This includes both development and production account portal domains, as well as FAPI domains
 * used for redirect-based authentication flows.
 * Determines if the referrer URL is from a Clerk domain: the instance's FAPI domain, the accounts
 * portal derived from its frontend API, or — on non-production instances only — a development
 * account-portal domain.
 *
 * @returns {boolean} True if the referrer is from a Clerk accounts portal or FAPI domain, false otherwise
 * @returns {boolean} True if the referrer is a trusted Clerk domain, false otherwise
 */
 public isKnownClerkReferrer(): boolean {
 if (!this.referrer) {
Expand All@@ -239,12 +239,16 @@ class AuthenticateContext implements AuthenticateContext {
 }
 }

 // Check for development account portal patterns
 if (isLegacyDevAccountPortalOrigin(referrerHost) || isCurrentDevAccountPortalOrigin(referrerHost)) {
 // Dev account-portal domains are freely obtainable, so only trust them on non-production instances.
 if (
 this.instanceType !== 'production' &&
 (isLegacyDevAccountPortalOrigin(referrerHost) || isCurrentDevAccountPortalOrigin(referrerHost))
 ) {
 return true;
 }

 // Check for production account portal by comparing with expected accounts URL
 // Only trust the accounts portal derived from this instance's frontend API — never a
 // generic `accounts.*` prefix, which any attacker-controlled domain could match.
 const expectedAccountsUrl = buildAccountsBaseUrl(this.frontendApi);
 if (expectedAccountsUrl) {
 const expectedAccountsOrigin = new URL(expectedAccountsUrl).origin;
Expand All@@ -253,11 +257,6 @@ class AuthenticateContext implements AuthenticateContext {
 }
 }

 // Check for generic production accounts patterns (accounts.*)
 if (referrerHost.startsWith('accounts.')) {
 return true;
 }

 return false;
 } catch {
 // Invalid URL format
Expand Down
Loading

, '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('^' + ".*" + '

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fix(backend): Fix cross-origin handshake bypass#9145

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 Merged

dominic-clerk
merged 3 commits into

from

Jul 18, 2026
 Merged


fix(backend): Fix cross-origin handshake bypass
#9145
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67c3fdc

fix(backend): Fix cross-origin handshake bypass


dominic-clerk Jul 13, 2026
9bee8e1

Address review comments


dominic-clerk Jul 13, 2026
0cd1824

Merge branch 'main' into dominic/sec-322-cross-origin-handshake-bypas…


wobsoriano Jul 17, 2026

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5 changes: 5 additions & 0 deletions
.changeset/khaki-chairs-kiss.md

View file


Open in desktop

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

Fix a cross-origin handshake bypass where `isKnownClerkReferrer()` trusted overly broad referrer hosts as Clerk-owned: any `accounts.*` host (e.g. `accounts.attacker.com`), plus dev account-portal domains (`*.accounts.dev` and legacy suffixes) on production instances. These let unrelated origins skip the handshake and its session-freshness check. The referrer is now trusted only for the accounts portal derived from the instance's frontend API, plus dev account-portal domains on non-production instances.

76 changes: 69 additions & 7 deletions
packages/backend/src/tokens/__tests__/request.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -2085,7 +2085,8 @@ describe('tokens.authenticateRequest(options)', () => {
 });
 });

 test('does not trigger handshake when referer is from production accounts portal', async () => {
@dominic-clerkdominic-clerkJul 13, 2026

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ContributorAuthor
Choose a reason for hiding this comment

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

We revert the logic of this test because it tested that example.com's account portal wouldn't trigger a handshake on another (primary.com's) instance.
 // accounts.example.com is not this instance's derived accounts portal, so it must not be trusted.
 test('triggers handshake when referer is an unrelated accounts.* domain', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://accounts.example.com/sign-in',
Expand All@@ -2107,14 +2108,14 @@ describe('tokens.authenticateRequest(options)', () => {
 signInUrl: 'https://primary.com/sign-in',
 });

 expect(requestState).toBeSignedIn({
 expect(requestState).toMatchHandshake({
 reason: AuthErrorReason.PrimaryDomainCrossOriginSync,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
 });
 });

 test('does not trigger handshake when referer is from dev accounts portal (current format)', async () => {
 test('does not trigger cross-origin handshake when referer is from dev accounts portal on a dev instance (current format)', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://foo-bar-13.accounts.dev/sign-in',
Expand All@@ -2124,13 +2125,14 @@ describe('tokens.authenticateRequest(options)', () => {
 {
 __session: mockJwt,
 __client_uat: '12345',
 __clerk_db_jwt: mockJwt,
 },
 'https://primary.com/dashboard',
 );

 const requestState = await authenticateRequest(request, {
 ...mockOptions(),
 publishableKey: PK_LIVE,
 publishableKey: PK_TEST,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
Expand All@@ -2143,7 +2145,7 @@ describe('tokens.authenticateRequest(options)', () => {
 });
 });

 test('does not trigger handshake when referer is from dev accounts portal (legacy format)', async () => {
 test('does not trigger cross-origin handshake when referer is from dev accounts portal on a dev instance (legacy format)', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://accounts.foo-bar-13.lcl.dev/sign-in',
Expand All@@ -2153,13 +2155,14 @@ describe('tokens.authenticateRequest(options)', () => {
 {
 __session: mockJwt,
 __client_uat: '12345',
 __clerk_db_jwt: mockJwt,
 },
 'https://primary.com/dashboard',
 );

 const requestState = await authenticateRequest(request, {
 ...mockOptions(),
 publishableKey: PK_LIVE,
 publishableKey: PK_TEST,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
Expand All@@ -2172,6 +2175,65 @@ describe('tokens.authenticateRequest(options)', () => {
 });
 });

 // A production instance must not trust dev-portal referrers, which are freely obtainable.
 test('triggers handshake when referer is a dev accounts portal on a production instance (current format)', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://foo-bar-13.accounts.dev/sign-in',
 'sec-fetch-dest': 'document',
 'sec-fetch-site': 'cross-site',
 },
 {
 __session: mockJwt,
 __client_uat: '12345',
 },
 'https://primary.com/dashboard',
 );

 const requestState = await authenticateRequest(request, {
 ...mockOptions(),
 publishableKey: PK_LIVE,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
 });

 expect(requestState).toMatchHandshake({
 reason: AuthErrorReason.PrimaryDomainCrossOriginSync,
 domain: 'primary.com',
 signInUrl: 'https://primary.com/sign-in',
 });
 });

 test('triggers handshake when referer is a dev accounts portal on a production instance (legacy format)', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://accounts.foo-bar-13.lcl.dev/sign-in',
 'sec-fetch-dest': 'document',
 'sec-fetch-site': 'cross-site',
 },
 {
 __session: mockJwt,
 __client_uat: '12345',
 },
 'https://primary.com/dashboard',
 );

 const requestState = await authenticateRequest(request, {
 ...mockOptions(),
 publishableKey: PK_LIVE,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
 });

 expect(requestState).toMatchHandshake({
 reason: AuthErrorReason.PrimaryDomainCrossOriginSync,
 domain: 'primary.com',
 signInUrl: 'https://primary.com/sign-in',
 });
 });

 test('does not trigger cross-origin handshake when referer is from expected accounts portal derived from frontend API', async () => {
 const request = mockRequestWithCookies(
 {
Expand Down

23 changes: 11 additions & 12 deletions
packages/backend/src/tokens/authenticateContext.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -216,11 +216,11 @@ class AuthenticateContext implements AuthenticateContext {
 }

 /**
 * Determines if the referrer URL is from a Clerk domain (accounts portal or FAPI).
 * This includes both development and production account portal domains, as well as FAPI domains
 * used for redirect-based authentication flows.
 * Determines if the referrer URL is from a Clerk domain: the instance's FAPI domain, the accounts
 * portal derived from its frontend API, or — on non-production instances only — a development
 * account-portal domain.
 *
 * @returns {boolean} True if the referrer is from a Clerk accounts portal or FAPI domain, false otherwise
 * @returns {boolean} True if the referrer is a trusted Clerk domain, false otherwise
 */
 public isKnownClerkReferrer(): boolean {
 if (!this.referrer) {
Expand All@@ -239,12 +239,16 @@ class AuthenticateContext implements AuthenticateContext {
 }
 }

 // Check for development account portal patterns
 if (isLegacyDevAccountPortalOrigin(referrerHost) || isCurrentDevAccountPortalOrigin(referrerHost)) {
 // Dev account-portal domains are freely obtainable, so only trust them on non-production instances.
 if (
 this.instanceType !== 'production' &&
 (isLegacyDevAccountPortalOrigin(referrerHost) || isCurrentDevAccountPortalOrigin(referrerHost))
 ) {
 return true;
 }

 // Check for production account portal by comparing with expected accounts URL
 // Only trust the accounts portal derived from this instance's frontend API — never a
 // generic `accounts.*` prefix, which any attacker-controlled domain could match.
 const expectedAccountsUrl = buildAccountsBaseUrl(this.frontendApi);
 if (expectedAccountsUrl) {
 const expectedAccountsOrigin = new URL(expectedAccountsUrl).origin;
Expand All@@ -253,11 +257,6 @@ class AuthenticateContext implements AuthenticateContext {
 }
 }

 // Check for generic production accounts patterns (accounts.*)
 if (referrerHost.startsWith('accounts.')) {
 return true;
 }

 return false;
 } catch {
 // Invalid URL format
Expand Down
Loading

, '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); }
})();
})();

Skip to content
fix(backend): Fix cross-origin handshake bypass#9145

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

Already on GitHub?
Sign in
to your account

 Merged

dominic-clerk
merged 3 commits into

from

Jul 18, 2026
 Merged


fix(backend): Fix cross-origin handshake bypass
#9145
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67c3fdc

fix(backend): Fix cross-origin handshake bypass


dominic-clerk Jul 13, 2026
9bee8e1

Address review comments


dominic-clerk Jul 13, 2026
0cd1824

Merge branch 'main' into dominic/sec-322-cross-origin-handshake-bypas…


wobsoriano Jul 17, 2026

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5 changes: 5 additions & 0 deletions
.changeset/khaki-chairs-kiss.md

View file


Open in desktop

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

Fix a cross-origin handshake bypass where `isKnownClerkReferrer()` trusted overly broad referrer hosts as Clerk-owned: any `accounts.*` host (e.g. `accounts.attacker.com`), plus dev account-portal domains (`*.accounts.dev` and legacy suffixes) on production instances. These let unrelated origins skip the handshake and its session-freshness check. The referrer is now trusted only for the accounts portal derived from the instance's frontend API, plus dev account-portal domains on non-production instances.

76 changes: 69 additions & 7 deletions
packages/backend/src/tokens/__tests__/request.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -2085,7 +2085,8 @@ describe('tokens.authenticateRequest(options)', () => {
 });
 });

 test('does not trigger handshake when referer is from production accounts portal', async () => {
@dominic-clerkdominic-clerkJul 13, 2026

Copy link


Copy Markdown

ContributorAuthor
Choose a reason for hiding this comment

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

We revert the logic of this test because it tested that example.com's account portal wouldn't trigger a handshake on another (primary.com's) instance.
 // accounts.example.com is not this instance's derived accounts portal, so it must not be trusted.
 test('triggers handshake when referer is an unrelated accounts.* domain', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://accounts.example.com/sign-in',
Expand All@@ -2107,14 +2108,14 @@ describe('tokens.authenticateRequest(options)', () => {
 signInUrl: 'https://primary.com/sign-in',
 });

 expect(requestState).toBeSignedIn({
 expect(requestState).toMatchHandshake({
 reason: AuthErrorReason.PrimaryDomainCrossOriginSync,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
 });
 });

 test('does not trigger handshake when referer is from dev accounts portal (current format)', async () => {
 test('does not trigger cross-origin handshake when referer is from dev accounts portal on a dev instance (current format)', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://foo-bar-13.accounts.dev/sign-in',
Expand All@@ -2124,13 +2125,14 @@ describe('tokens.authenticateRequest(options)', () => {
 {
 __session: mockJwt,
 __client_uat: '12345',
 __clerk_db_jwt: mockJwt,
 },
 'https://primary.com/dashboard',
 );

 const requestState = await authenticateRequest(request, {
 ...mockOptions(),
 publishableKey: PK_LIVE,
 publishableKey: PK_TEST,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
Expand All@@ -2143,7 +2145,7 @@ describe('tokens.authenticateRequest(options)', () => {
 });
 });

 test('does not trigger handshake when referer is from dev accounts portal (legacy format)', async () => {
 test('does not trigger cross-origin handshake when referer is from dev accounts portal on a dev instance (legacy format)', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://accounts.foo-bar-13.lcl.dev/sign-in',
Expand All@@ -2153,13 +2155,14 @@ describe('tokens.authenticateRequest(options)', () => {
 {
 __session: mockJwt,
 __client_uat: '12345',
 __clerk_db_jwt: mockJwt,
 },
 'https://primary.com/dashboard',
 );

 const requestState = await authenticateRequest(request, {
 ...mockOptions(),
 publishableKey: PK_LIVE,
 publishableKey: PK_TEST,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
Expand All@@ -2172,6 +2175,65 @@ describe('tokens.authenticateRequest(options)', () => {
 });
 });

 // A production instance must not trust dev-portal referrers, which are freely obtainable.
 test('triggers handshake when referer is a dev accounts portal on a production instance (current format)', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://foo-bar-13.accounts.dev/sign-in',
 'sec-fetch-dest': 'document',
 'sec-fetch-site': 'cross-site',
 },
 {
 __session: mockJwt,
 __client_uat: '12345',
 },
 'https://primary.com/dashboard',
 );

 const requestState = await authenticateRequest(request, {
 ...mockOptions(),
 publishableKey: PK_LIVE,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
 });

 expect(requestState).toMatchHandshake({
 reason: AuthErrorReason.PrimaryDomainCrossOriginSync,
 domain: 'primary.com',
 signInUrl: 'https://primary.com/sign-in',
 });
 });

 test('triggers handshake when referer is a dev accounts portal on a production instance (legacy format)', async () => {
 const request = mockRequestWithCookies(
 {
 referer: 'https://accounts.foo-bar-13.lcl.dev/sign-in',
 'sec-fetch-dest': 'document',
 'sec-fetch-site': 'cross-site',
 },
 {
 __session: mockJwt,
 __client_uat: '12345',
 },
 'https://primary.com/dashboard',
 );

 const requestState = await authenticateRequest(request, {
 ...mockOptions(),
 publishableKey: PK_LIVE,
 domain: 'primary.com',
 isSatellite: false,
 signInUrl: 'https://primary.com/sign-in',
 });

 expect(requestState).toMatchHandshake({
 reason: AuthErrorReason.PrimaryDomainCrossOriginSync,
 domain: 'primary.com',
 signInUrl: 'https://primary.com/sign-in',
 });
 });

 test('does not trigger cross-origin handshake when referer is from expected accounts portal derived from frontend API', async () => {
 const request = mockRequestWithCookies(
 {
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23 changes: 11 additions & 12 deletions
packages/backend/src/tokens/authenticateContext.ts

View file


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Original file line numberDiff line numberDiff line change
Expand Up@@ -216,11 +216,11 @@ class AuthenticateContext implements AuthenticateContext {
 }

 /**
 * Determines if the referrer URL is from a Clerk domain (accounts portal or FAPI).
 * This includes both development and production account portal domains, as well as FAPI domains
 * used for redirect-based authentication flows.
 * Determines if the referrer URL is from a Clerk domain: the instance's FAPI domain, the accounts
 * portal derived from its frontend API, or — on non-production instances only — a development
 * account-portal domain.
 *
 * @returns {boolean} True if the referrer is from a Clerk accounts portal or FAPI domain, false otherwise
 * @returns {boolean} True if the referrer is a trusted Clerk domain, false otherwise
 */
 public isKnownClerkReferrer(): boolean {
 if (!this.referrer) {
Expand All@@ -239,12 +239,16 @@ class AuthenticateContext implements AuthenticateContext {
 }
 }

 // Check for development account portal patterns
 if (isLegacyDevAccountPortalOrigin(referrerHost) || isCurrentDevAccountPortalOrigin(referrerHost)) {
 // Dev account-portal domains are freely obtainable, so only trust them on non-production instances.
 if (
 this.instanceType !== 'production' &&
 (isLegacyDevAccountPortalOrigin(referrerHost) || isCurrentDevAccountPortalOrigin(referrerHost))
 ) {
 return true;
 }

 // Check for production account portal by comparing with expected accounts URL
 // Only trust the accounts portal derived from this instance's frontend API — never a
 // generic `accounts.*` prefix, which any attacker-controlled domain could match.
 const expectedAccountsUrl = buildAccountsBaseUrl(this.frontendApi);
 if (expectedAccountsUrl) {
 const expectedAccountsOrigin = new URL(expectedAccountsUrl).origin;
Expand All@@ -253,11 +257,6 @@ class AuthenticateContext implements AuthenticateContext {
 }
 }

 // Check for generic production accounts patterns (accounts.*)
 if (referrerHost.startsWith('accounts.')) {
 return true;
 }

 return false;
 } catch {
 // Invalid URL format
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