CVE-2026-40487: CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in gitroomhq postiz-app
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.
AI Analysis
Technical Summary
Postiz-app before version 2.21.6 contains a vulnerability where file upload validation can be bypassed by authenticated users spoofing the Content-Type header, allowing upload of executable files such as HTML or SVG. These files are served by nginx with content types derived from their extensions, enabling stored cross-site scripting (CWE-79) attacks. This vulnerability can result in session riding, account takeover, and full compromise of other users' accounts. The issue is tracked as CVE-2026-40487 with a CVSS 3.1 score of 8.9 (high severity). The vulnerability is fixed in version 2.21.6.
Potential Impact
Successful exploitation allows authenticated users to upload malicious executable files that are served and executed in the context of the application's origin. This can lead to session riding, account takeover, and full compromise of other users' accounts. The vulnerability affects confidentiality and integrity with high impact and availability with low impact.
Mitigation Recommendations
Upgrade postiz-app to version 2.21.6 or later, where this vulnerability has been fixed. Since the vulnerability requires authenticated user access and is resolved in the updated version, applying this official fix is the recommended remediation.
CVE-2026-40487: CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in gitroomhq postiz-app
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 v3.1
Score 8.9high
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
Postiz-app before version 2.21.6 contains a vulnerability where file upload validation can be bypassed by authenticated users spoofing the Content-Type header, allowing upload of executable files such as HTML or SVG. These files are served by nginx with content types derived from their extensions, enabling stored cross-site scripting (CWE-79) attacks. This vulnerability can result in session riding, account takeover, and full compromise of other users' accounts. The issue is tracked as CVE-2026-40487 with a CVSS 3.1 score of 8.9 (high severity). The vulnerability is fixed in version 2.21.6.
Potential Impact
Successful exploitation allows authenticated users to upload malicious executable files that are served and executed in the context of the application's origin. This can lead to session riding, account takeover, and full compromise of other users' accounts. The vulnerability affects confidentiality and integrity with high impact and availability with low impact.
Mitigation Recommendations
Upgrade postiz-app to version 2.21.6 or later, where this vulnerability has been fixed. Since the vulnerability requires authenticated user access and is resolved in the updated version, applying this official fix is the recommended remediation.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-04-13T19:50:42.114Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 69e2e080bdfbbecc59c723ab
Added to database: 4/18/2026, 1:38:08 AM
Last enriched: 4/25/2026, 2:54:50 AM
Last updated: 6/2/2026, 1:10:48 AM
Views: 101
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