CVE-2026-40487: Gitroom Postiz

Critical severity, CVSS 9.0. EPSS: 0.3% chance of exploitation in the next 30 days.

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.

Affected products

• Gitroom Postiz: before 2.21.6 (fixed in 2.21.6)

Published 2026-04-18. Last modified 2026-06-17.