CVE-2021-40100: Concretecms Concrete CMS

Medium severity, CVSS 5.4. EPSS: 0.5% chance of exploitation in the next 30 days.

An issue was discovered in Concrete CMS through 8.5.5. Stored XSS can occur in Conversations when the Active Conversation Editor is set to Rich Text.

Affected products

• Concretecms Concrete CMS: up to and including 8.5.5

Published 2021-09-24. Last modified 2026-06-17.