NIST deprecates RSA-2048 from 2030. Find every one of them before attackers do.
🐹
🐹 Go
Not in CISA KEV
HIGH severity

FileBrowser Quantum: Stored XSS in public share page via unsanitized share metadata (text/template misuse)GHSA-r633-fcgp-m532

HIGH

GHSA-r633-fcgp-m532 is a high-severity (CVSS 8.9) Cross-site Scripting (XSS) vulnerability in github.com/gtsteffaniak/filebrowser. A fix is available for github.com/gtsteffaniak/filebrowser — see the affected versions and patch details below.

Also known asCVE-2026-30934GO-2026-4660
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Nov 7, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

  • CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
  • A successful exploit gives an attacker total control of the affected component, not partial access.

Exploitation and automatability from CISA’s SSVC triage for GHSA-r633-fcgp-m532.

EPSS Exploitation Probability

via FIRST.org ↗
0.4%probability of exploitation in next 30 days
Lower Risk+0.05%
Lower risk than most CVEs36th percentile — riskier than 36% of all scored CVEsHighest risk
0.00%0.30%0.61%0.91%0.0%0.4%May 26Aug 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected
🐹github.com/gtsteffaniak/filebrowser

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

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 metadata:
    • title = </title><script>alert("xss")</script><title>
  3. Open the resulting /public/share/<hash> URL in a browser.
  4. Expected: Payload is safely escaped and displayed as text.
  5. 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.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐹Gogithub.com/gtsteffaniak/filebrowserall versions0.0.0-20260307130210-09713b32a5f6go get github.com/gtsteffaniak/filebrowser@v0.0.0-20260307130210-09713b32a5f6

Affected Products

1 product · 3 configurations
Application
filebrowserfilebrowser
≤ 1.2.9
2 versions
1.2.11.3.0

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/gtsteffaniak/filebrowser, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update github.com/gtsteffaniak/filebrowser to 0.0.0-20260307130210-09713b32a5f6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-r633-fcgp-m532 is resolved across your whole dependency graph.

  3. Workarounds

    Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

## 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 be
O3 Security · Impact-Aware SCA

Is GHSA-r633-fcgp-m532 in your dependencies?

Find it across Go, including transitive dependencies.

Scan my dependencies How O3 SCA works
FileBrowser Quantum: Stored XSS in public share page…