XSS in Gitroom Postiz
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.
Vulnerability class: XSS (Cross-Site Scripting)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.9 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:L.
EPSS exploit prediction
EPSS: 0.002 (13.3th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 13th percentile — 13.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: 0.000
Affected products
- Gitroom Postiz
- Gitroomhq Postiz-App — versions < 2.21.6
Weakness classification (CWE)
Public proof-of-concept exploits
References
- github.com/gitroomhq/postiz-app/security/advisories/GHSA-44wg-r34q-hvfx (Exploit, Vendor Advisory)
- github.com/gitroomhq/postiz-app/releases/tag/v2.21.6 (Product, Release Notes)
Frequently asked questions
- What is CVE-2026-40487?
- CVE-2026-40487 is a high-severity vulnerability in Gitroom Postiz, classified under Cross-site Scripting. CVSS score: 8.9/10. Published 2026-04-18.
- How severe is CVE-2026-40487?
- High severity. CVSS v3 base score is 8.9 out of 10.
- Is CVE-2026-40487 known to be exploited?
- 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.