CVE-2026-81900 Concrete CMS before 9.5.3 is vulnerable to Stored XSS in the YouTube block (vWidth/vHeight)

Concrete CMS before 9.5.3 applied only trim to the YouTube block's stored width and height values and printed them into iframe HTML attributes without escaping or integer casting, resulting in stored cross-site scripting. A user with editblock permission could inject an event handler that execute...