CVE-2026-40487

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.

Score

CVSS 3.1 9.0 Critical

Status

Analyzed - security-advisories@github.com

Published

2026-04-18

Last modified

2026-10-26

Weaknesses

CWE-345, CWE-434, CWE-79

Affected products

• Postiz (Gitroom)
• Postiz-app (Gitroomhq)

References

• https://github.com/gitroomhq/postiz-app/security/advisories/GHSA-44wg-r34q-hvfx
• https://github.com/gitroomhq/postiz-app/releases/tag/v2.21.6