CVE-2021-23836: Flatcore

Medium severity, CVSS 4.8. EPSS: 0.9% chance of exploitation in the next 30 days.

An issue was discovered in flatCore before 2.0.0 build 139. A stored XSS vulnerability was identified in the prefs_smtp_psw HTTP request body parameter for the acp interface. An admin user can inject malicious client-side script into the affected parameter without any form of input sanitization. The injected payload will be executed in the browser of a user whenever one visits the affected module page.

Affected products

• Flatcore Flatcore: up to and including 2.0.0

Published 2021-01-15. Last modified 2026-06-17.