🛡️ Sentinel: [HIGH] Fix XSS vulnerability in description preview#15
🛡️ Sentinel: [HIGH] Fix XSS vulnerability in description preview#15
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Identified a Cross-Site Scripting (XSS) vulnerability in `src/components/upload/DescriptionPreview.tsx` where user-provided HTML from the backend or BBCode was rendered using `dangerouslySetInnerHTML` without proper sanitization (only `{}` placeholders were removed).
This commit mitigates the issue by introducing `isomorphic-dompurify` to sanitize all rendered HTML while maintaining proper Server-Side Rendering (SSR) functionality to prevent hydration mismatches in the Astro/Preact frontend. A journal entry was also added to `.jules/sentinel.md` documenting this security learning.
Co-authored-by: bobdivx <6737167+bobdivx@users.noreply.github.com>
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Summary of ChangesHello, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed! This pull request significantly enhances the application's security posture by resolving a critical XSS vulnerability in the description preview functionality. The core of the solution involves implementing a robust HTML sanitization library, Highlights
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Code Review
This pull request effectively addresses a critical Cross-Site Scripting (XSS) vulnerability by introducing isomorphic-dompurify to sanitize user-provided HTML content before rendering. The choice of an isomorphic library is well-suited for the Astro/Preact architecture, ensuring consistent sanitization on both the server and client. The inclusion of a learning entry in the Sentinel journal is also a commendable practice for knowledge sharing. I have one suggestion to further improve the robustness of the sanitization logic.
| const cleanedHtml = DOMPurify.sanitize(html); | ||
| return cleanedHtml.replace(/\{\}/g, ''); |
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For better robustness and a more logical flow, it's preferable to remove the {} placeholders before sanitizing the HTML. This ensures that DOMPurify operates on the string that is closest to the final output, preventing any potential edge cases where the sanitization process might interfere with placeholder removal (e.g., by encoding characters).
| const cleanedHtml = DOMPurify.sanitize(html); | |
| return cleanedHtml.replace(/\{\}/g, ''); | |
| return DOMPurify.sanitize(html.replace(/\{\}/g, '')); |
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🛡️ Sentinel: [HIGH] Fix XSS vulnerability in description preview
🚨 Severity
HIGH
💡 Vulnerability
A Cross-Site Scripting (XSS) vulnerability was found in
src/components/upload/DescriptionPreview.tsx. User-provided content (either via thehtmlorrawBBCode props) was rendered using Preact'sdangerouslySetInnerHTMLwithout proper sanitization. The previous sanitization only removed{}placeholders but did not sanitize malicious tags or attributes (e.g.,<img src="x" onerror="alert(1)">).🎯 Impact
Malicious users could potentially inject arbitrary JavaScript into the application through the
htmlorrawBBCode content, leading to session hijacking, data theft, or execution of actions on behalf of the victim.🔧 Fix
Introduced
isomorphic-dompurifyto sanitize the HTML output before rendering it withdangerouslySetInnerHTML. Because this is an Astro/Preact application,isomorphic-dompurifyensures that DOM sanitization is performed both on the client side and the server side, which is necessary to avoid SSR hydration mismatches. Added the learning to.jules/sentinel.mdjournal.✅ Verification
npm test) continues to pass.onerror) are properly stripped.PR created automatically by Jules for task 3535897701096353591 started by @bobdivx