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...

CVE-2026-81900

Concrete CMS before 9.5.3 is affected by a stored cross-site scripting vulnerability in the YouTube block (vWidth/vHeight). The root cause is that only trim() was applied to the stored width and height values before printing them into iframe HTML attributes , without escaping or integer casting. ...