🛡️ Sentinel: [HIGH] Fix XSS vulnerability in DescriptionPreview

[bobdivx]

🚨 Severity: HIGH
💡 Vulnerability: The DescriptionPreview component used dangerouslySetInnerHTML to render user-provided HTML and converted BBCode descriptions without any sanitization, leading to a potential Cross-Site Scripting (XSS) vulnerability.
🎯 Impact: An attacker could craft a malicious description containing executable JavaScript (e.g., via <script> tags or onerror handlers). When another user views this description, the malicious script would execute in their context, potentially leading to session hijacking, unauthorized actions, or data theft.
🔧 Fix: Introduced isomorphic-dompurify and wrapped all HTML output injected via dangerouslySetInnerHTML in DOMPurify.sanitize(). isomorphic-dompurify was chosen over standard dompurify to prevent window is not defined errors during Astro/Preact Server-Side Rendering (SSR). Also added a unit test to verify that onerror handlers and other XSS vectors are successfully stripped.
✅ Verification: npm run test src/components/upload/DescriptionPreview.test.ts passes. npm run build succeeds without SSR errors.

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PR created automatically by Jules for task 15717903538753576247 started by @bobdivx

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Project	Deployment	Actions	Updated (UTC)
popcorn-client	Ready	Preview, Comment	Mar 25, 2026 7:47am

[gemini-code-assist]

Summary of Changes

Hello, 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 improves the application's security by resolving a high-severity XSS vulnerability within the DescriptionPreview component. The fix involves implementing robust HTML sanitization using isomorphic-dompurify to prevent the execution of malicious scripts from user-generated content, thereby protecting users from potential session hijacking or data theft.

Highlights

• XSS Vulnerability Addressed: A high-severity Cross-Site Scripting (XSS) vulnerability in the DescriptionPreview component was fixed, which previously allowed unsanitized user-provided HTML and BBCode to be rendered.
• Sanitization with isomorphic-dompurify: The isomorphic-dompurify library was integrated to sanitize all HTML output before it is rendered using dangerouslySetInnerHTML, ensuring compatibility with Server-Side Rendering (SSR) environments like Astro/Preact.
• Enhanced Test Coverage: A new unit test was added specifically to DescriptionPreview.test.ts to validate that common XSS vectors, such as onerror handlers, are effectively stripped by the sanitization process.

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[gemini-code-assist]

Code Review

This pull request focuses on implementing XSS mitigation in the DescriptionPreview component by integrating isomorphic-dompurify. It includes adding isomorphic-dompurify, @playwright/test, and preact-render-to-string as dependencies, updating various other dependencies, and introducing new tests to verify the XSS prevention. The core change involves sanitizing HTML content using DOMPurify.sanitize() before rendering it with dangerouslySetInnerHTML in DescriptionPreview.tsx.