CVE-2026-81924 – Concrete CMS before 9.5.3 is vulnerable to Cross-Site Request Forgery (CSRF) in the theme

Concrete CMS before 9.5.3 is vulnerable to Cross-Site Request Forgery (CSRF) in the theme page-template activation feature. The Dashboard theme Inspect controller’s activate_files() action created PageTemplate records from attacker-supplied pageTemplates[] values without validating an anti-CSRF token.A remote attacker could host a page that auto-submitted a forged POST request; when a signed-in administrator visited it, the request executed under the administrator’s session and created theme page-template records, changing site configuration without the administrator’s consent. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 2.1 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N. Thanks Andrew Gonzalez for reporting.