Critical severity · published Apr 18, 2026
CVE-2026-40487
Postiz Has Unrestricted File Upload via MIME Type Spoofing that Leads to Stored XSS
9.0
CVSS
0.2%
EPSS
No
On KEV
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 vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
Required
Confidentiality
High
Integrity
High
Availability
High
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 13% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
PO
postiz-app · gitroomhq
< 2.21.6 · source: vendor
PO
Postiz · Gitroom
before 2.21.6 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-40487
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-40487
Product
https://github.com/gitroomhq/postiz-app/releases/tag/v2.21.6
Exploit
https://github.com/gitroomhq/postiz-app/security/advisories/GHSA-44wg-r34q-hvfx
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