Security: ZekStack/seal

Security

docs/security.md

Security

Seal v0.1 is a JWT/JWS library, not an encryption library.

JWT headers and payloads are base64url encoded, not encrypted. Anyone holding a token can decode and read its claims.

Verification Is Mandatory

decode() does not verify signatures. Use verify() before trusting any value from a token.

HS256 Secrets

HS256 uses one shared secret for signing and verification. If the secret is weak, leaked, or extracted, attackers can forge valid tokens.

Use high-entropy secrets and rotate them when compromise is possible.

Embedded Secret Risk

Secrets stored in firmware can be extracted when physical compromise is in scope. Seal can validate token integrity, but it cannot protect a secret that is available to an attacker through device extraction.

Expiration Requires Time

exp, nbf, and maxAgeSeconds validation require a valid epoch clock. If time is required and unavailable, Seal returns SealCode::ClockUnavailable.

exp is expired at the exact expiration timestamp when clock tolerance is zero. nbf and maxAgeSeconds use the configured clockToleranceSeconds without additive timestamp overflow.

Header Behavior

Seal requires alg to be exactly HS256. The typ header is ignored by default, so tokens from issuers that use different typ casing or values can still verify when the algorithm, signature, JSON payload, and claims are valid.

Crypto Backend Boundary

Production v0.1 crypto uses mbedTLS behind SealCrypto.h. This boundary exists so the backend can be replaced later without changing the public Seal API.

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: ZekStack/seal
Security

docs/security.md

Security
Seal v0.1 is a JWT/JWS library, not an encryption library.
JWT headers and payloads are base64url encoded, not encrypted. Anyone holding a token can decode and read its claims.
Verification Is Mandatory
decode() does not verify signatures. Use verify() before trusting any value from a token.
HS256 Secrets
HS256 uses one shared secret for signing and verification. If the secret is weak, leaked, or extracted, attackers can forge valid tokens.
Use high-entropy secrets and rotate them when compromise is possible.
Embedded Secret Risk
Secrets stored in firmware can be extracted when physical compromise is in scope. Seal can validate token integrity, but it cannot protect a secret that is available to an attacker through device extraction.
Expiration Requires Time
exp, nbf, and maxAgeSeconds validation require a valid epoch clock. If time is required and unavailable, Seal returns SealCode::ClockUnavailable.
exp is expired at the exact expiration timestamp when clock tolerance is zero. nbf and maxAgeSeconds use the configured clockToleranceSeconds without additive timestamp overflow.
Header Behavior
Seal requires alg to be exactly HS256. The typ header is ignored by default, so tokens from issuers that use different typ casing or values can still verify when the algorithm, signature, JSON payload, and claims are valid.
Crypto Backend Boundary
Production v0.1 crypto uses mbedTLS behind SealCrypto.h. This boundary exists so the backend can be replaced later without changing the public Seal API.
 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: ZekStack/seal
Security

docs/security.md

Security
Seal v0.1 is a JWT/JWS library, not an encryption library.
JWT headers and payloads are base64url encoded, not encrypted. Anyone holding a token can decode and read its claims.
Verification Is Mandatory
decode() does not verify signatures. Use verify() before trusting any value from a token.
HS256 Secrets
HS256 uses one shared secret for signing and verification. If the secret is weak, leaked, or extracted, attackers can forge valid tokens.
Use high-entropy secrets and rotate them when compromise is possible.
Embedded Secret Risk
Secrets stored in firmware can be extracted when physical compromise is in scope. Seal can validate token integrity, but it cannot protect a secret that is available to an attacker through device extraction.
Expiration Requires Time
exp, nbf, and maxAgeSeconds validation require a valid epoch clock. If time is required and unavailable, Seal returns SealCode::ClockUnavailable.
exp is expired at the exact expiration timestamp when clock tolerance is zero. nbf and maxAgeSeconds use the configured clockToleranceSeconds without additive timestamp overflow.
Header Behavior
Seal requires alg to be exactly HS256. The typ header is ignored by default, so tokens from issuers that use different typ casing or values can still verify when the algorithm, signature, JSON payload, and claims are valid.
Crypto Backend Boundary
Production v0.1 crypto uses mbedTLS behind SealCrypto.h. This boundary exists so the backend can be replaced later without changing the public Seal API.
 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: ZekStack/seal
Security

docs/security.md

Security
Seal v0.1 is a JWT/JWS library, not an encryption library.
JWT headers and payloads are base64url encoded, not encrypted. Anyone holding a token can decode and read its claims.
Verification Is Mandatory
decode() does not verify signatures. Use verify() before trusting any value from a token.
HS256 Secrets
HS256 uses one shared secret for signing and verification. If the secret is weak, leaked, or extracted, attackers can forge valid tokens.
Use high-entropy secrets and rotate them when compromise is possible.
Embedded Secret Risk
Secrets stored in firmware can be extracted when physical compromise is in scope. Seal can validate token integrity, but it cannot protect a secret that is available to an attacker through device extraction.
Expiration Requires Time
exp, nbf, and maxAgeSeconds validation require a valid epoch clock. If time is required and unavailable, Seal returns SealCode::ClockUnavailable.
exp is expired at the exact expiration timestamp when clock tolerance is zero. nbf and maxAgeSeconds use the configured clockToleranceSeconds without additive timestamp overflow.
Header Behavior
Seal requires alg to be exactly HS256. The typ header is ignored by default, so tokens from issuers that use different typ casing or values can still verify when the algorithm, signature, JSON payload, and claims are valid.
Crypto Backend Boundary
Production v0.1 crypto uses mbedTLS behind SealCrypto.h. This boundary exists so the backend can be replaced later without changing the public Seal API.
 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: ZekStack/seal
Security

docs/security.md

Security
Seal v0.1 is a JWT/JWS library, not an encryption library.
JWT headers and payloads are base64url encoded, not encrypted. Anyone holding a token can decode and read its claims.
Verification Is Mandatory
decode() does not verify signatures. Use verify() before trusting any value from a token.
HS256 Secrets
HS256 uses one shared secret for signing and verification. If the secret is weak, leaked, or extracted, attackers can forge valid tokens.
Use high-entropy secrets and rotate them when compromise is possible.
Embedded Secret Risk
Secrets stored in firmware can be extracted when physical compromise is in scope. Seal can validate token integrity, but it cannot protect a secret that is available to an attacker through device extraction.
Expiration Requires Time
exp, nbf, and maxAgeSeconds validation require a valid epoch clock. If time is required and unavailable, Seal returns SealCode::ClockUnavailable.
exp is expired at the exact expiration timestamp when clock tolerance is zero. nbf and maxAgeSeconds use the configured clockToleranceSeconds without additive timestamp overflow.
Header Behavior
Seal requires alg to be exactly HS256. The typ header is ignored by default, so tokens from issuers that use different typ casing or values can still verify when the algorithm, signature, JSON payload, and claims are valid.
Crypto Backend Boundary
Production v0.1 crypto uses mbedTLS behind SealCrypto.h. This boundary exists so the backend can be replaced later without changing the public Seal API.
 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: ZekStack/seal
Security

docs/security.md

Security
Seal v0.1 is a JWT/JWS library, not an encryption library.
JWT headers and payloads are base64url encoded, not encrypted. Anyone holding a token can decode and read its claims.
Verification Is Mandatory
decode() does not verify signatures. Use verify() before trusting any value from a token.
HS256 Secrets
HS256 uses one shared secret for signing and verification. If the secret is weak, leaked, or extracted, attackers can forge valid tokens.
Use high-entropy secrets and rotate them when compromise is possible.
Embedded Secret Risk
Secrets stored in firmware can be extracted when physical compromise is in scope. Seal can validate token integrity, but it cannot protect a secret that is available to an attacker through device extraction.
Expiration Requires Time
exp, nbf, and maxAgeSeconds validation require a valid epoch clock. If time is required and unavailable, Seal returns SealCode::ClockUnavailable.
exp is expired at the exact expiration timestamp when clock tolerance is zero. nbf and maxAgeSeconds use the configured clockToleranceSeconds without additive timestamp overflow.
Header Behavior
Seal requires alg to be exactly HS256. The typ header is ignored by default, so tokens from issuers that use different typ casing or values can still verify when the algorithm, signature, JSON payload, and claims are valid.
Crypto Backend Boundary
Production v0.1 crypto uses mbedTLS behind SealCrypto.h. This boundary exists so the backend can be replaced later without changing the public Seal API.
 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: ZekStack/seal
Security

docs/security.md

Security
Seal v0.1 is a JWT/JWS library, not an encryption library.
JWT headers and payloads are base64url encoded, not encrypted. Anyone holding a token can decode and read its claims.
Verification Is Mandatory
decode() does not verify signatures. Use verify() before trusting any value from a token.
HS256 Secrets
HS256 uses one shared secret for signing and verification. If the secret is weak, leaked, or extracted, attackers can forge valid tokens.
Use high-entropy secrets and rotate them when compromise is possible.
Embedded Secret Risk
Secrets stored in firmware can be extracted when physical compromise is in scope. Seal can validate token integrity, but it cannot protect a secret that is available to an attacker through device extraction.
Expiration Requires Time
exp, nbf, and maxAgeSeconds validation require a valid epoch clock. If time is required and unavailable, Seal returns SealCode::ClockUnavailable.
exp is expired at the exact expiration timestamp when clock tolerance is zero. nbf and maxAgeSeconds use the configured clockToleranceSeconds without additive timestamp overflow.
Header Behavior
Seal requires alg to be exactly HS256. The typ header is ignored by default, so tokens from issuers that use different typ casing or values can still verify when the algorithm, signature, JSON payload, and claims are valid.
Crypto Backend Boundary
Production v0.1 crypto uses mbedTLS behind SealCrypto.h. This boundary exists so the backend can be replaced later without changing the public Seal API.
 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: ZekStack/seal
Security

docs/security.md

Security
Seal v0.1 is a JWT/JWS library, not an encryption library.
JWT headers and payloads are base64url encoded, not encrypted. Anyone holding a token can decode and read its claims.
Verification Is Mandatory
decode() does not verify signatures. Use verify() before trusting any value from a token.
HS256 Secrets
HS256 uses one shared secret for signing and verification. If the secret is weak, leaked, or extracted, attackers can forge valid tokens.
Use high-entropy secrets and rotate them when compromise is possible.
Embedded Secret Risk
Secrets stored in firmware can be extracted when physical compromise is in scope. Seal can validate token integrity, but it cannot protect a secret that is available to an attacker through device extraction.
Expiration Requires Time
exp, nbf, and maxAgeSeconds validation require a valid epoch clock. If time is required and unavailable, Seal returns SealCode::ClockUnavailable.
exp is expired at the exact expiration timestamp when clock tolerance is zero. nbf and maxAgeSeconds use the configured clockToleranceSeconds without additive timestamp overflow.
Header Behavior
Seal requires alg to be exactly HS256. The typ header is ignored by default, so tokens from issuers that use different typ casing or values can still verify when the algorithm, signature, JSON payload, and claims are valid.
Crypto Backend Boundary
Production v0.1 crypto uses mbedTLS behind SealCrypto.h. This boundary exists so the backend can be replaced later without changing the public Seal API.
 There aren't any published security advisories