High Severity Vulnerability
This vulnerability has been rated as High severity. Immediate action is recommended.
CVE-2026-40487
HighVulnerability 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.
CVSS Metrics
Common Vulnerability Scoring System
Vector String:
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:L
Severity Details
Weakness Type (CWE)
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
- Description
- The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.
- Exploit Likelihood
- High
- Typical Severity
- Medium
- OWASP Top 10
- A03:2021-Injection
- Abstraction Level
- Base
Key Information
- Published Date
- April 18, 2026
