CVE-2026-40487 — Postiz Has Unrestricted File Upload via MIME Type Spoofing that Leads to Stored XSS
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 exec…
Published: 2026-04-18 · CVSS: 8.9 · CVSS 3.1
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.
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7