🐛 Fix XSS Vulnerability in SVG Upload Handling #19646
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This commit introduces DOMPurify as a dependency to sanitize SVG files during upload. SVG files can potentially contain malicious code leading to Cross-Site Scripting (XSS) vulnerabilities. By sanitizing SVG content with DOMPurify, we mitigate the risk of XSS, enhancing the security of the Ghost CMS platform. - Added `dompurify` and `jsdom` to `package.json` dependencies for server-side DOM emulation and sanitization. - Updated file validation logic to include SVG sanitization in `upload.js`. - Ensured that all SVG files are checked and sanitized before being saved or processed further. - Added relevant documentation in `README.md` and `CONTRIBUTING.md` to guide developers on the necessity and usage of DOMPurify for handling SVG uploads. This security measure is crucial for protecting both the Ghost CMS platform and its users from potential XSS attacks through SVG file uploads. While DOMPurify aims to sanitize SVG files thoroughly, it's configured to strike a balance between security and usability, ensuring valid SVG files remain functional after sanitization.
This commit addresses a vulnerability by integrating DOMPurify to sanitize SVG file uploads, preventing potential XSS attacks within Ghost CMS. The changes made in the `update.js` file ensure that all SVG files undergo a sanitization process before being processed or stored. Key Changes: - Integrated DOMPurify within `update.js` to sanitize SVG files against XSS vulnerabilities. - Added `jsdom` to emulate a DOM environment for DOMPurify to operate in a server-side context. - Updated the SVG file validation workflow to include a sanitization step using DOMPurify, ensuring SVG files are clean before acceptance. - Ensured backward compatibility and non-disruption of existing functionalities by selectively applying sanitization only to SVG files.
Fixed syntax causing errors.
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If the sanitized SVG content is then served via an SVG file (meaning Because if not, we introduce namespace confusion and could be prone to mXSS. for example, in a normal parsing (as done in DOMPurify): |
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@TeneBrae93 Thanks for the comprehensive report and proposed fix! I've merged a PR here. |
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This PR addresses a vulnerability in the handling of SVG file uploads (especially in staff profile pictures) within Ghost CMS. By integrating DOMPurify, we ensure that SVG files are sanitized to remove potential XSS attacks, enhancing the security of the platform without affecting the core functionalities.
Changes Made:
update.js.package.jsonto includedompurifyas a dependency, ensuring the sanitization process is robust and effective.Impact:
Testing:
This fix contributes to the ongoing effort to maintain and improve the security posture of Ghost CMS, ensuring it remains a safe and reliable platform for users and developers alike.
Additional Notes:
security@ghost.orgbut was declined since staff are trusted users. This PR will fix the core issue and prevent XSS in SVG uploads.Thank you for considering this contribution to enhance Ghost CMS's security.