CVE-2026-40487

Postiz Has Unrestricted File Upload via MIME Type Spoofing that Leads to Stored XSS

State: Published
Severity: 8.9 High
Published: Apr 18, 2026
Updated: Apr 20, 2026
Reserved: Apr 13, 2026

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.

Scores

CVSS	Score	Vector	Source
3.1	8.9 High	CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:L	GitHub_M

Weaknesses

CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CWE-345 Insufficient Verification of Data Authenticity
CWE-434 Unrestricted Upload of File with Dangerous Type

Affected Products

Product	Versions
postiz-appgitroomhq	< 2.21.6Affected

References

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