CVE-2026-18117: Concrete CMS 9.0.0 to 9.5.2 is vulnerable to Stored XSS in Custom Page Alias Name
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.
Affected Software
Event History
Frequently Asked Questions
Who can exploit this issue, and who is exposed to the payload?
An authenticated user with canWrite (editor) permission on a page can create the malicious alias. Administrators and editors are exposed when they open the administrative Sitemap panel that renders the stored alias.
What interaction is required for the stored script to run?
The malicious alias executes automatically when an administrator or editor opens the Sitemap panel where the alias is rendered. The attacker does not need to be present when the victim opens the panel.
What could a successful attack allow?
The issue can let an editor escalate to administrator by executing code in an administrator's or editor's active session. The reported impact includes high confidentiality and integrity effects and low availability impact.