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

• Go github.com/gtsteffaniak/filebrowser: < 0.0.0-20260307130210-09713b32a5f6 → fixed in 0.0.0-20260307130210-09713b32a5f6

Summary Stored XSS is possible via share metadata fields (e.g., `title`, `description`) that are rendered into HTML for `/public/share/` 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 = alert("xss")` 3. Open the resulting `/public/share/` 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.