CVE-2026-81900

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 edit_block permission could inject an event handler that executed script for visitors rendering the page, acting with administrative privileges where the victim was an administrator. 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:H/SC:N/SI:N/SA:N. Thanks sh4d0byss for reporting.

CVSS

No CVSS.

References

Link	Resource
https://documentation.concretecms.org/developers/introduction/version-history/953-release-notes

Configurations

No configuration.

History

No history.

Information

Published : 2026-09-14 23:18

Updated : 2026-09-15 14:40

NVD link : CVE-2026-81900

Mitre link : CVE-2026-81900

CVE.ORG link : CVE-2026-81900

JSON object : View

Products Affected

No product.

CWE

CWE-79

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

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