CVE-2026-18117

Concrete CMS 9.0.0 through 9.5.3 is vulnerable to stored XSS via the custom page alias name (customAliasName) because the Edit Alias dialog applied only trim() to the submitted value and performed no input neutralization. An authenticated user holding canWrite (editor) permission on a page could store a malicious alias name that was later rendered unescaped in the administrative Sitemap panel, where it executed automatically in any administrator or editor session that opened the panel, allowing an editor to escalate to administrator through the victim's active session. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 7.3 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N. Thanks Nguyen Manh Thuan for reporting.