CVE-2023-28820: Concretecms Concrete CMS

Medium severity, CVSS 5.4. EPSS: 0.4% chance of exploitation in the next 30 days.

Concrete CMS (previously concrete5) before 9.1 is vulnerable to stored XSS in RSS Displayer via the href attribute because the link element input was not sanitized.

Affected products

• Concretecms Concrete CMS: before 9.1.0 (fixed in 9.1.0)

Published 2023-04-28. Last modified 2026-06-17.