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fix(coding-agent): sanitize markdown links in exported session HTML (#3532)

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marked v15 does not filter dangerous URL protocols. The default link
renderer passes href values through verbatim, so markdown like
`[click](javascript:alert(1))` renders as a clickable XSS link in
shared/exported session HTML.

Add custom link and image renderers that:
- Block javascript:, vbscript:, and data: protocol URLs
- Escape href/title/alt attributes via escapeHtml()

Also escape img.mimeType in session image rendering to prevent
attribute breakout from crafted session JSONL.

Fixes #3531
This commit is contained in:
Samuel Painter
2026-04-22 01:53:03 -07:00
committed by GitHub
parent 9f91276a42
commit ee462dd70d
2 changed files with 56 additions and 2 deletions
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30
packages/coding-agent/src/core/export-html/template.js
View File

@@ -881,7 +881,7 @@
const images = getResultImages();
if (images.length === 0) return '';
return '<div class="tool-images">' +
images.map(img => `<img src="data:${img.mimeType};base64,${img.data}" class="tool-image" />`).join('') +
images.map(img => `<img src="data:${escapeHtml(img.mimeType || 'image/png')};base64,${img.data}" class="tool-image" />`).join('') +
'</div>';
};
@@ -1148,7 +1148,7 @@
if (images.length > 0) {
html += '<div class="message-images">';
for (const img of images) {
html += `<img src="data:${img.mimeType};base64,${img.data}" class="message-image" />`;
html += `<img src="data:${escapeHtml(img.mimeType || 'image/png')};base64,${img.data}" class="message-image" />`;
}
html += '</div>';
}
@@ -1491,6 +1491,32 @@
}
},
renderer: {
// Sanitize link URLs to prevent javascript:/vbscript:/data: XSS
link(token) {
const href = (token.href || '').trim();
if (/^\s*(javascript|vbscript|data):/i.test(href)) {
return this.parser.parseInline(token.tokens);
}
let out = '<a href="' + escapeHtml(href) + '"';
if (token.title) {
out += ' title="' + escapeHtml(token.title) + '"';
}
out += '>' + this.parser.parseInline(token.tokens) + '</a>';
return out;
},
// Sanitize image src URLs
image(token) {
const href = (token.href || '').trim();
if (/^\s*(javascript|vbscript|data):/i.test(href)) {
return escapeHtml(token.text || '');
}
let out = '<img src="' + escapeHtml(href) + '" alt="' + escapeHtml(token.text || '') + '"';
if (token.title) {
out += ' title="' + escapeHtml(token.title) + '"';
}
out += '>';
return out;
},
// Code blocks: syntax highlight, no HTML escaping
code(token) {
const code = token.text;