CVE-2026-30948

Workarounds

Configure the fileExtensions option to explicitly block SVG uploads:

{
  fileUpload: {
    fileExtensions: ['^(?!([xXsS]?[hH][tT][mM][lL]?|[sS][vV][gG])$)']
  }
}

References

• GitHub security advisory: https://github.com/parse-community/parse-server/security/advisories/GHSA-hcj7-6gxh-24ww
• Fix Parse Server 9: https://github.com/parse-community/parse-server/releases/tag/9.5.2-alpha.4
• Fix Parse Server 8: https://github.com/parse-community/parse-server/releases/tag/8.6.17

A stored cross-site scripting (XSS) vulnerability allows any authenticated user to upload an SVG file containing JavaScript. The file is served inline with Content-Type: image/svg+xml and without protective headers, causing the browser to execute embedded scripts in the Parse Server origin. This can be exploited to steal session tokens from localStorage and achieve account takeover.

The default fileExtensions option blocks HTML file extensions but does not block SVG, which is a well-known XSS vector. All Parse Server deployments where file upload is enabled for authenticated users (the default) are affected.

Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.

Kodem intelligence

The fix adds svg (case-insensitive) to the default file extension denylist. The default regex changes from ^(?![xXsS]?[hH][tT][mM][lL]?$) to ^(?!([xXsS]?[hH][tT][mM][lL]?|[sS][vV][gG])$).

1. What is CVE-2026-30948? CVE-2026-30948 is a high-severity cross-site scripting (XSS) vulnerability in parse-server (npm), affecting versions >= 9.0.0, < 9.5.2-alpha.4. It is fixed in 9.5.2-alpha.4, 8.6.17. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
2. Which versions of parse-server are affected by CVE-2026-30948? parse-server (npm) versions >= 9.0.0, < 9.5.2-alpha.4 is affected.
3. Is there a fix for CVE-2026-30948? Yes. CVE-2026-30948 is fixed in 9.5.2-alpha.4, 8.6.17. Upgrade to this version or later.
4. Is CVE-2026-30948 exploitable, and should I be worried? Whether CVE-2026-30948 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
5. What actually determines whether CVE-2026-30948 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
6. How do I fix CVE-2026-30948?
   • Upgrade parse-server to 9.5.2-alpha.4 or later
   • Upgrade parse-server to 8.6.17 or later

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