Summary
FileBrowser Quantum: Stored XSS in public share page via unsanitized share metadata (text/template misuse)
Stored XSS is possible via share metadata fields (e.g., title, description) that are rendered into HTML for /public/share/<hash> without context-aware escaping. The server uses text/template instead of html/template, allowing injected scripts to execute when victims visit the share URL.
Details
The server renders public/index.html using text/template and injects user-controlled share fields (title/description/etc.) into HTML contexts. text/template does not perform HTML contextual escaping like html/template. Because share metadata is persistent, the payload becomes stored and executes whenever a victim opens the affected share page.
Relevant code paths:
backend/http/static.go(template rendering and share metadata assignment)backend/http/httpRouter.go(template initialization)frontend/public/index.html(insertion points for title/description and related fields)
PoC
- Login as a user with share creation permission.
- Create a share (
POST /api/share) with malicious metadata:title = </title><script>alert("xss")</script><title>
- Open the resulting
/public/share/<hash>URL in a browser. - Expected: Payload is safely escaped and displayed as text.
- Actual: JavaScript executes in victim's browser (stored XSS).
Tested on Docker image: gtstef/filebrowser:stable (version v1.2.1-stable).
Impact
- Arbitrary script execution in application origin.
- Potential account/session compromise, CSRF-like action execution, data exfiltration from authenticated contexts.
- Affects anyone (including unauthenticated visitors) opening the malicious share URL.
- The XSS is stored and persistent, no social engineering beyond sharing the link is required.
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.
CVE-2026-30934 has a CVSS score of 8.9 (High). The vector is network-reachable, low privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.0.0-20260307130210-09713b32a5f6); upgrading removes the vulnerable code path.
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.
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Frequently Asked Questions
- What is CVE-2026-30934? CVE-2026-30934 is a high-severity cross-site scripting (XSS) vulnerability in github.com/gtsteffaniak/filebrowser (go), affecting versions < 0.0.0-20260307130210-09713b32a5f6. It is fixed in 0.0.0-20260307130210-09713b32a5f6. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
- How severe is CVE-2026-30934? CVE-2026-30934 has a CVSS score of 8.9 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of github.com/gtsteffaniak/filebrowser are affected by CVE-2026-30934? github.com/gtsteffaniak/filebrowser (go) versions < 0.0.0-20260307130210-09713b32a5f6 is affected.
- Is there a fix for CVE-2026-30934? Yes. CVE-2026-30934 is fixed in 0.0.0-20260307130210-09713b32a5f6. Upgrade to this version or later.
- Is CVE-2026-30934 exploitable, and should I be worried? Whether CVE-2026-30934 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-2026-30934 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-2026-30934? Upgrade
github.com/gtsteffaniak/filebrowserto 0.0.0-20260307130210-09713b32a5f6 or later.