FileBrowser Quantum: Stored XSS in public share page via unsanitized share metadata (text/template misuse)

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

8.9 · CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:L

EPSS

• CVE-2026-30934: 0.37% estimated exploitation activity in the next 30 days; percentile 30.75 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary 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 1. Login as a user with share creation permission. 2. Create a share (POST /api/share) with malicious…

Published by the source

9 Mar 2026, 19:48 UTC

Last modified by the source

24 Mar 2026, 21:09 UTC

Source last checked

26 Oct 2026, 15:18 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-r633-fcgp-m532

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# Patch Next advisory brief: CVE-2026-30934

Advisory: FileBrowser Quantum: Stored XSS in public share page via unsanitized share metadata (text/template misuse)
IDs: CVE-2026-30934, GHSA-r633-fcgp-m532
Record: https://patchnext.com/advisories/cve-2026-30934 (revision 1, source checked 26 Oct 2026, 15:18 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/gtsteffaniak/filebrowser 0.0.0-20260307130210-09713b32a5f6. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/gtsteffaniak/filebrowser: affected < 0.0.0-20260307130210-09713b32a5f6; fixed in 0.0.0-20260307130210-09713b32a5f6

## Suggested inspection (read-only)
- Go github.com/gtsteffaniak/filebrowser: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/gtsteffaniak/filebrowser.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-r633-fcgp-m532 (GitHub-reviewed advisory GHSA-r633-fcgp-m532 lists affected ranges: Go github.com/gtsteffaniak/filebrowser >=0 <0.0.0-20260307130210-09713b32a5f6)

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