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GHSA-r633-fcgp-m532

HighCVSS 8.9 / 10
Published Mar 9, 2026·Last modified Mar 24, 2026
Affected Components(0)

No affected components available

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.
Risk Scores
Base Score
8.9

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. The attacker needs the user to perform some action, like clicking a link. The vulnerability can affect other systems as well, not just the initial system. There is a high impact on the confidentiality of the information. There is a high impact on the integrity of the data. There is a low impact on the availability of the system.

Threat Intelligence
8.1

Exploitation activity has been observed. Apply available patches or mitigations urgently.

EPSS
0.35%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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High severity
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