Postiz is an AI social media scheduling tool. Prior to version 2.21.6, a file upload validation bypass allows any authenticated user to upload arbitrary HTML, SVG, or other executable file types to the server by spoofing the `Content-Type` header. The uploaded files are then served by nginx with a Content-Type derived from their original extension (`text/html`, `image/svg+xml`), enabling Stored Cross-Site Scripting (XSS) in the context of the application's origin. This can lead to session riding, account takeover, and full compromise of other users' accounts. Version 2.21.6 contains a fix.
Fix
Public exploits 1
- Astaruf/CVE-2026-40487 PoC on GitHub
Each line links to the index that lists it, never to exploit code. Exploit-DB's "verified" and a Metasploit rank of good or better count as verified; a PoC-in-GitHub entry is a repository's claim.
Patch, vendor advisory and mitigation references on NVD 2
- https://github.com/gitroomhq/postiz-app/security/advisories/GHSA-44wg-r34q-hvfx Exploit, Vendor Advisory
- https://github.com/gitroomhq/postiz-app/security/advisories/GHSA-44wg-r34q-hvfx Exploit, Vendor Advisory
Every line above is quoted from NVD, CISA, Microsoft, the vendor's own advisory or DISA; nothing is generated.
Change history 1
- First seenCVSS 9.0 · gitroomNVD modified 2026-10-26 21:10
Affected (CPE criteria) 1
cpe:2.3:a:gitroom:postiz:*:*:*:*:*:*:*:*
References 3
- https://github.com/gitroomhq/postiz-app/releases/tag/v2.21.6 Product, Release Notes
- https://github.com/gitroomhq/postiz-app/security/advisories/GHSA-44wg-r34q-hvfx Exploit, Vendor Advisory
- https://github.com/gitroomhq/postiz-app/security/advisories/GHSA-44wg-r34q-hvfx Exploit, Vendor Advisory