Security: useFormseal/embed

Security

Report a vulnerability

.github/SECURITY.md

Security

Report vulnerabilities privately via the "Report a vulnerability" button on this repo's Security tab. Do not open a public issue. Include a description, steps to reproduce, and potential impact.

What formseal-embed protects

  • Interception in transit — submissions are encrypted before transport. Passive network observers cannot read payload contents without the private key.
  • Server-side data leaks — plaintext is not exposed to backend proxies, logging middleware, or server-side analytics after encryption occurs in the browser.
  • Storage breaches — ciphertext requires the private key to decrypt. For strongest isolation, private keys should not reside on machines handling inbound submissions.
  • Runtime tampering resistance — critical config and crypto modules are frozen after initialization to reduce accidental or late-stage mutation by third-party scripts.

What it does NOT protect

  • Compromised client — malware on user's device reads keystrokes before encryption.
  • Malicious host pages — the page embedding formseal-embed can intercept user input before encryption occurs.
  • Wrong endpoint — encryption does not authenticate the destination. Submissions sent to an attacker-controlled endpoint remain encrypted, but the attacker can store or forward the ciphertext.
  • Stolen private key — all past and future submissions become readable.

Supply chain and JS delivery

Client-side encryption cannot protect against malicious JavaScript delivered before encryption occurs. An attacker who compromises the npm package, CDN, hosting, build pipeline, or embedding page can steal plaintext before it is encrypted.

Requirements

  • HTTPS required — refuses to run on HTTP (except localhost/127.0.0.1 in development).

Encryption

  • Algorithm: X25519 (libsodium sealed box)
  • Keys: 32-byte public/private pair, base64url encoded
  • Scope: entire payload encrypted as one blob

Key hygiene

  • Never commit the private key to version control.
  • Store it as an environment variable or secrets manager.
  • Keep it off any machine that handles inbound submissions — decrypt separately.

Threat model

formseal-embed is a client-side browser library. It assumes the user's browser is not compromised and the embedding page is trusted. It does not protect against malicious host pages, compromised build pipelines, or stolen private keys.

There aren't any published security advisories

, '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
Security: useFormseal/embed
Security
Report a vulnerability

.github/SECURITY.md

Security
Report vulnerabilities privately via the "Report a vulnerability" button on this repo's Security tab. Do not open a public issue. Include a description, steps to reproduce, and potential impact.
What formseal-embed protects
  • Interception in transit — submissions are encrypted before transport. Passive network observers cannot read payload contents without the private key.
  • Server-side data leaks — plaintext is not exposed to backend proxies, logging middleware, or server-side analytics after encryption occurs in the browser.
  • Storage breaches — ciphertext requires the private key to decrypt. For strongest isolation, private keys should not reside on machines handling inbound submissions.
  • Runtime tampering resistance — critical config and crypto modules are frozen after initialization to reduce accidental or late-stage mutation by third-party scripts.
What it does NOT protect
  • Compromised client — malware on user's device reads keystrokes before encryption.
  • Malicious host pages — the page embedding formseal-embed can intercept user input before encryption occurs.
  • Wrong endpoint — encryption does not authenticate the destination. Submissions sent to an attacker-controlled endpoint remain encrypted, but the attacker can store or forward the ciphertext.
  • Stolen private key — all past and future submissions become readable.
Supply chain and JS delivery
Client-side encryption cannot protect against malicious JavaScript delivered before encryption occurs. An attacker who compromises the npm package, CDN, hosting, build pipeline, or embedding page can steal plaintext before it is encrypted.
Requirements
  • HTTPS required — refuses to run on HTTP (except localhost/127.0.0.1 in development).
Encryption
  • Algorithm: X25519 (libsodium sealed box)
  • Keys: 32-byte public/private pair, base64url encoded
  • Scope: entire payload encrypted as one blob
Key hygiene
  • Never commit the private key to version control.
  • Store it as an environment variable or secrets manager.
  • Keep it off any machine that handles inbound submissions — decrypt separately.
Threat model
formseal-embed is a client-side browser library. It assumes the user's browser is not compromised and the embedding page is trusted. It does not protect against malicious host pages, compromised build pipelines, or stolen private keys.
 There aren't any published security advisories


, '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
Security: useFormseal/embed
Security
Report a vulnerability

.github/SECURITY.md

Security
Report vulnerabilities privately via the "Report a vulnerability" button on this repo's Security tab. Do not open a public issue. Include a description, steps to reproduce, and potential impact.
What formseal-embed protects
  • Interception in transit — submissions are encrypted before transport. Passive network observers cannot read payload contents without the private key.
  • Server-side data leaks — plaintext is not exposed to backend proxies, logging middleware, or server-side analytics after encryption occurs in the browser.
  • Storage breaches — ciphertext requires the private key to decrypt. For strongest isolation, private keys should not reside on machines handling inbound submissions.
  • Runtime tampering resistance — critical config and crypto modules are frozen after initialization to reduce accidental or late-stage mutation by third-party scripts.
What it does NOT protect
  • Compromised client — malware on user's device reads keystrokes before encryption.
  • Malicious host pages — the page embedding formseal-embed can intercept user input before encryption occurs.
  • Wrong endpoint — encryption does not authenticate the destination. Submissions sent to an attacker-controlled endpoint remain encrypted, but the attacker can store or forward the ciphertext.
  • Stolen private key — all past and future submissions become readable.
Supply chain and JS delivery
Client-side encryption cannot protect against malicious JavaScript delivered before encryption occurs. An attacker who compromises the npm package, CDN, hosting, build pipeline, or embedding page can steal plaintext before it is encrypted.
Requirements
  • HTTPS required — refuses to run on HTTP (except localhost/127.0.0.1 in development).
Encryption
  • Algorithm: X25519 (libsodium sealed box)
  • Keys: 32-byte public/private pair, base64url encoded
  • Scope: entire payload encrypted as one blob
Key hygiene
  • Never commit the private key to version control.
  • Store it as an environment variable or secrets manager.
  • Keep it off any machine that handles inbound submissions — decrypt separately.
Threat model
formseal-embed is a client-side browser library. It assumes the user's browser is not compromised and the embedding page is trusted. It does not protect against malicious host pages, compromised build pipelines, or stolen private keys.
 There aren't any published security advisories


, '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
Security: useFormseal/embed
Security
Report a vulnerability

.github/SECURITY.md

Security
Report vulnerabilities privately via the "Report a vulnerability" button on this repo's Security tab. Do not open a public issue. Include a description, steps to reproduce, and potential impact.
What formseal-embed protects
  • Interception in transit — submissions are encrypted before transport. Passive network observers cannot read payload contents without the private key.
  • Server-side data leaks — plaintext is not exposed to backend proxies, logging middleware, or server-side analytics after encryption occurs in the browser.
  • Storage breaches — ciphertext requires the private key to decrypt. For strongest isolation, private keys should not reside on machines handling inbound submissions.
  • Runtime tampering resistance — critical config and crypto modules are frozen after initialization to reduce accidental or late-stage mutation by third-party scripts.
What it does NOT protect
  • Compromised client — malware on user's device reads keystrokes before encryption.
  • Malicious host pages — the page embedding formseal-embed can intercept user input before encryption occurs.
  • Wrong endpoint — encryption does not authenticate the destination. Submissions sent to an attacker-controlled endpoint remain encrypted, but the attacker can store or forward the ciphertext.
  • Stolen private key — all past and future submissions become readable.
Supply chain and JS delivery
Client-side encryption cannot protect against malicious JavaScript delivered before encryption occurs. An attacker who compromises the npm package, CDN, hosting, build pipeline, or embedding page can steal plaintext before it is encrypted.
Requirements
  • HTTPS required — refuses to run on HTTP (except localhost/127.0.0.1 in development).
Encryption
  • Algorithm: X25519 (libsodium sealed box)
  • Keys: 32-byte public/private pair, base64url encoded
  • Scope: entire payload encrypted as one blob
Key hygiene
  • Never commit the private key to version control.
  • Store it as an environment variable or secrets manager.
  • Keep it off any machine that handles inbound submissions — decrypt separately.
Threat model
formseal-embed is a client-side browser library. It assumes the user's browser is not compromised and the embedding page is trusted. It does not protect against malicious host pages, compromised build pipelines, or stolen private keys.
 There aren't any published security advisories


, '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
Security: useFormseal/embed
Security
Report a vulnerability

.github/SECURITY.md

Security
Report vulnerabilities privately via the "Report a vulnerability" button on this repo's Security tab. Do not open a public issue. Include a description, steps to reproduce, and potential impact.
What formseal-embed protects
  • Interception in transit — submissions are encrypted before transport. Passive network observers cannot read payload contents without the private key.
  • Server-side data leaks — plaintext is not exposed to backend proxies, logging middleware, or server-side analytics after encryption occurs in the browser.
  • Storage breaches — ciphertext requires the private key to decrypt. For strongest isolation, private keys should not reside on machines handling inbound submissions.
  • Runtime tampering resistance — critical config and crypto modules are frozen after initialization to reduce accidental or late-stage mutation by third-party scripts.
What it does NOT protect
  • Compromised client — malware on user's device reads keystrokes before encryption.
  • Malicious host pages — the page embedding formseal-embed can intercept user input before encryption occurs.
  • Wrong endpoint — encryption does not authenticate the destination. Submissions sent to an attacker-controlled endpoint remain encrypted, but the attacker can store or forward the ciphertext.
  • Stolen private key — all past and future submissions become readable.
Supply chain and JS delivery
Client-side encryption cannot protect against malicious JavaScript delivered before encryption occurs. An attacker who compromises the npm package, CDN, hosting, build pipeline, or embedding page can steal plaintext before it is encrypted.
Requirements
  • HTTPS required — refuses to run on HTTP (except localhost/127.0.0.1 in development).
Encryption
  • Algorithm: X25519 (libsodium sealed box)
  • Keys: 32-byte public/private pair, base64url encoded
  • Scope: entire payload encrypted as one blob
Key hygiene
  • Never commit the private key to version control.
  • Store it as an environment variable or secrets manager.
  • Keep it off any machine that handles inbound submissions — decrypt separately.
Threat model
formseal-embed is a client-side browser library. It assumes the user's browser is not compromised and the embedding page is trusted. It does not protect against malicious host pages, compromised build pipelines, or stolen private keys.
 There aren't any published security advisories


, '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
Security: useFormseal/embed
Security
Report a vulnerability

.github/SECURITY.md

Security
Report vulnerabilities privately via the "Report a vulnerability" button on this repo's Security tab. Do not open a public issue. Include a description, steps to reproduce, and potential impact.
What formseal-embed protects
  • Interception in transit — submissions are encrypted before transport. Passive network observers cannot read payload contents without the private key.
  • Server-side data leaks — plaintext is not exposed to backend proxies, logging middleware, or server-side analytics after encryption occurs in the browser.
  • Storage breaches — ciphertext requires the private key to decrypt. For strongest isolation, private keys should not reside on machines handling inbound submissions.
  • Runtime tampering resistance — critical config and crypto modules are frozen after initialization to reduce accidental or late-stage mutation by third-party scripts.
What it does NOT protect
  • Compromised client — malware on user's device reads keystrokes before encryption.
  • Malicious host pages — the page embedding formseal-embed can intercept user input before encryption occurs.
  • Wrong endpoint — encryption does not authenticate the destination. Submissions sent to an attacker-controlled endpoint remain encrypted, but the attacker can store or forward the ciphertext.
  • Stolen private key — all past and future submissions become readable.
Supply chain and JS delivery
Client-side encryption cannot protect against malicious JavaScript delivered before encryption occurs. An attacker who compromises the npm package, CDN, hosting, build pipeline, or embedding page can steal plaintext before it is encrypted.
Requirements
  • HTTPS required — refuses to run on HTTP (except localhost/127.0.0.1 in development).
Encryption
  • Algorithm: X25519 (libsodium sealed box)
  • Keys: 32-byte public/private pair, base64url encoded
  • Scope: entire payload encrypted as one blob
Key hygiene
  • Never commit the private key to version control.
  • Store it as an environment variable or secrets manager.
  • Keep it off any machine that handles inbound submissions — decrypt separately.
Threat model
formseal-embed is a client-side browser library. It assumes the user's browser is not compromised and the embedding page is trusted. It does not protect against malicious host pages, compromised build pipelines, or stolen private keys.
 There aren't any published security advisories


, '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
Security: useFormseal/embed
Security
Report a vulnerability

.github/SECURITY.md

Security
Report vulnerabilities privately via the "Report a vulnerability" button on this repo's Security tab. Do not open a public issue. Include a description, steps to reproduce, and potential impact.
What formseal-embed protects
  • Interception in transit — submissions are encrypted before transport. Passive network observers cannot read payload contents without the private key.
  • Server-side data leaks — plaintext is not exposed to backend proxies, logging middleware, or server-side analytics after encryption occurs in the browser.
  • Storage breaches — ciphertext requires the private key to decrypt. For strongest isolation, private keys should not reside on machines handling inbound submissions.
  • Runtime tampering resistance — critical config and crypto modules are frozen after initialization to reduce accidental or late-stage mutation by third-party scripts.
What it does NOT protect
  • Compromised client — malware on user's device reads keystrokes before encryption.
  • Malicious host pages — the page embedding formseal-embed can intercept user input before encryption occurs.
  • Wrong endpoint — encryption does not authenticate the destination. Submissions sent to an attacker-controlled endpoint remain encrypted, but the attacker can store or forward the ciphertext.
  • Stolen private key — all past and future submissions become readable.
Supply chain and JS delivery
Client-side encryption cannot protect against malicious JavaScript delivered before encryption occurs. An attacker who compromises the npm package, CDN, hosting, build pipeline, or embedding page can steal plaintext before it is encrypted.
Requirements
  • HTTPS required — refuses to run on HTTP (except localhost/127.0.0.1 in development).
Encryption
  • Algorithm: X25519 (libsodium sealed box)
  • Keys: 32-byte public/private pair, base64url encoded
  • Scope: entire payload encrypted as one blob
Key hygiene
  • Never commit the private key to version control.
  • Store it as an environment variable or secrets manager.
  • Keep it off any machine that handles inbound submissions — decrypt separately.
Threat model
formseal-embed is a client-side browser library. It assumes the user's browser is not compromised and the embedding page is trusted. It does not protect against malicious host pages, compromised build pipelines, or stolen private keys.
 There aren't any published security advisories


, '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
Security: useFormseal/embed
Security
Report a vulnerability

.github/SECURITY.md

Security
Report vulnerabilities privately via the "Report a vulnerability" button on this repo's Security tab. Do not open a public issue. Include a description, steps to reproduce, and potential impact.
What formseal-embed protects
  • Interception in transit — submissions are encrypted before transport. Passive network observers cannot read payload contents without the private key.
  • Server-side data leaks — plaintext is not exposed to backend proxies, logging middleware, or server-side analytics after encryption occurs in the browser.
  • Storage breaches — ciphertext requires the private key to decrypt. For strongest isolation, private keys should not reside on machines handling inbound submissions.
  • Runtime tampering resistance — critical config and crypto modules are frozen after initialization to reduce accidental or late-stage mutation by third-party scripts.
What it does NOT protect
  • Compromised client — malware on user's device reads keystrokes before encryption.
  • Malicious host pages — the page embedding formseal-embed can intercept user input before encryption occurs.
  • Wrong endpoint — encryption does not authenticate the destination. Submissions sent to an attacker-controlled endpoint remain encrypted, but the attacker can store or forward the ciphertext.
  • Stolen private key — all past and future submissions become readable.
Supply chain and JS delivery
Client-side encryption cannot protect against malicious JavaScript delivered before encryption occurs. An attacker who compromises the npm package, CDN, hosting, build pipeline, or embedding page can steal plaintext before it is encrypted.
Requirements
  • HTTPS required — refuses to run on HTTP (except localhost/127.0.0.1 in development).
Encryption
  • Algorithm: X25519 (libsodium sealed box)
  • Keys: 32-byte public/private pair, base64url encoded
  • Scope: entire payload encrypted as one blob
Key hygiene
  • Never commit the private key to version control.
  • Store it as an environment variable or secrets manager.
  • Keep it off any machine that handles inbound submissions — decrypt separately.
Threat model
formseal-embed is a client-side browser library. It assumes the user's browser is not compromised and the embedding page is trusted. It does not protect against malicious host pages, compromised build pipelines, or stolen private keys.
 There aren't any published security advisories