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Vulnerability · Published Apr 18, 2026 · Assigned by GitHub_M

CVE-2026-40487Postiz Has Unrestricted File Upload via MIME Type Spoofing that Leads to Stored XSS

High 8.9

In plain English

A high-severity cross-site scripting in postiz-app from gitroomhq. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 13% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code.

Severity (CVSS 3.1)8.9High
Exploit odds (30 days)0.2%top 86.9% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack tooling1Public PoC

Official description

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 (as reported)

VendorProductVersions
gitroomhq postiz-app < 2.21.6

Weakness: CWE-79, CWE-345, CWE-434 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:L

References