Summary
Workarounds
Configure the fileUpload.fileExtensions server option to block the affected file extensions and content types.
References
- GitHub security advisory: https://github.com/parse-community/parse-server/security/advisories/GHSA-v5hf-f4c3-m5rv
- Fix Parse Server 9: https://github.com/parse-community/parse-server/releases/tag/9.6.0-alpha.4
- Fix Parse Server 8: https://github.com/parse-community/parse-server/releases/tag/8.6.30
Impact
An attacker can upload a file with a file extension or content type that is not blocked by the default configuration of the Parse Server fileUpload.fileExtensions option. The file can contain malicious code, for example JavaScript in an SVG or XHTML file. When the file is accessed via its URL, the browser renders the file and executes the malicious code in the context of the Parse Server domain. This is a stored Cross-Site Scripting (XSS) vulnerability that can be exploited to steal session tokens, redirect users, or perform actions on behalf of other users.
Affected file extensions and content types include .svgz, .xht, .xml, .xsl, .xslt, and content types application/xhtml+xml and application/xslt+xml for extensionless uploads. Uploading of .html, .htm, .shtml, .xhtml, and .svg files was already blocked.
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.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
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. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
The fix adds the missing file extensions and content types to the default value of the fileUpload.fileExtensions server option.
Frequently Asked Questions
- What is CVE-2026-31868? CVE-2026-31868 is a medium-severity cross-site scripting (XSS) vulnerability in parse-server (npm), affecting versions >= 9.0.0-alpha.1, < 9.6.0-alpha.4. It is fixed in 9.6.0-alpha.4, 8.6.30. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
- Which versions of parse-server are affected by CVE-2026-31868? parse-server (npm) versions >= 9.0.0-alpha.1, < 9.6.0-alpha.4 is affected.
- Is there a fix for CVE-2026-31868? Yes. CVE-2026-31868 is fixed in 9.6.0-alpha.4, 8.6.30. Upgrade to this version or later.
- Is CVE-2026-31868 exploitable, and should I be worried? Whether CVE-2026-31868 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
- What actually determines whether CVE-2026-31868 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.
- How do I fix CVE-2026-31868?
- Upgrade
parse-serverto 9.6.0-alpha.4 or later - Upgrade
parse-serverto 8.6.30 or later
- Upgrade