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Sanitizer: block data:/vbscript: URLs (XSS hardening) #42806

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Sanitizer: block data:/vbscript: URLs (XSS hardening) #42806

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538b4ef
Sanitizer: block data:/vbscript: URLs (XSS hardening)
aljojoby9 Aug 6, 2026
8c91b30
Sanitizer: allow audio/mpeg in DATA_URL_PATTERN
aljojoby9 Aug 6, 2026
b7be493
Document base64-only data URLs and tighten bundlewatch budgets
aljojoby9 Aug 11, 2026
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8 changes: 4 additions & 4 deletions .bundlewatch.config.json
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Original file line number Diff line number Diff line change
Expand Up @@ -34,27 +34,27 @@
},
{
"path": "./dist/js/bootstrap.bundle.js",
"maxSize": "43.0 kB"
"maxSize": "43.25 kB"
},
{
"path": "./dist/js/bootstrap.bundle.min.js",
"maxSize": "23.5 kB"
},
{
"path": "./dist/js/bootstrap.esm.js",
"maxSize": "28.0 kB"
"maxSize": "28.25 kB"
},
{
"path": "./dist/js/bootstrap.esm.min.js",
"maxSize": "18.25 kB"
},
{
"path": "./dist/js/bootstrap.js",
"maxSize": "28.75 kB"
"maxSize": "29.0 kB"
},
{
"path": "./dist/js/bootstrap.min.js",
"maxSize": "16.25 kB"
"maxSize": "16.5 kB"
}
],
"ci": {
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13 changes: 11 additions & 2 deletions js/src/util/sanitizer.js
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Original file line number Diff line number Diff line change
Expand Up @@ -63,14 +63,23 @@ const uriAttributes = new Set([
*
* Shout-out to Angular https://github.com/angular/angular/blob/15.2.8/packages/core/src/sanitization/url_sanitizer.ts#L38
*/
const SAFE_URL_PATTERN = /^(?!javascript:)(?:[a-z0-9+.-]+:|[^&:/?#]*(?:[/?#]|$))/i
const SAFE_URL_PATTERN = /^(?!(?:javascript|data|vbscript):)(?:[a-z0-9+.-]+:|[^&:/?#]*(?:[/?#]|$))/i

/**
* A pattern that matches safe data URLs. Only matches base64-encoded image,
* video and audio types — notably NOT `data:text/html`, and not non-base64
* media payloads (e.g. `data:image/png,...` without `;base64,`).
*
* Shout-out to Angular https://github.com/angular/angular/blob/15.2.8/packages/core/src/sanitization/url_sanitizer.ts#L49
*/
const DATA_URL_PATTERN = /^data:(?:image\/(?:bmp|gif|jpeg|jpg|png|tiff|webp)|video\/(?:mpeg|mp4|ogg|webm)|audio\/(?:mp3|mpeg|oga|ogg|opus));base64,[\d+/a-z=]+$/i

const allowedAttribute = (attribute, allowedAttributeList) => {
const attributeName = attribute.nodeName.toLowerCase()

if (allowedAttributeList.includes(attributeName)) {
if (uriAttributes.has(attributeName)) {
return Boolean(SAFE_URL_PATTERN.test(attribute.nodeValue))
return Boolean(SAFE_URL_PATTERN.test(attribute.nodeValue) || DATA_URL_PATTERN.test(attribute.nodeValue))
}

return true
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9 changes: 8 additions & 1 deletion js/tests/unit/util/sanitizer.spec.js
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Original file line number Diff line number Diff line change
Expand Up @@ -31,6 +31,7 @@ describe('Sanitizer', () => {
'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAYAAAAf8/', // Truncated.
'data:video/webm;base64,iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAYAAAAf8/',
'data:audio/opus;base64,iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAYAAAAf8/',
'data:audio/mpeg;base64,iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAYAAAAf8/',
'unknown-scheme:abc'
]

Expand Down Expand Up @@ -67,7 +68,13 @@ describe('Sanitizer', () => {
'jav\u0000ascript:alert();'
]

for (const url of invalidUrls) {
const dangerousDataUrls = [
'data:text/html,hello',
'data:text/html;base64,PHNjcmlwdD5hbGVydCgxKTwvc2NyaXB0Pg==',
'vbscript:msgbox(1)'
]

for (const url of [...invalidUrls, ...dangerousDataUrls]) {
const template = [
'<div>',
` <a href="${url}">Click me</a>`,
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