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.

Project Subscriptions

Vendors Products
Concretecms Subscribe
Concrete Cms Subscribe
Advisories

No advisories yet.

Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Tue, 15 Sep 2026 14:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}


Tue, 15 Sep 2026 08:15:00 +0000

Type Values Removed Values Added
First Time appeared Concretecms
Concretecms concrete Cms
Vendors & Products Concretecms
Concretecms concrete Cms

Mon, 14 Sep 2026 22:30:00 +0000

Type Values Removed Values Added
Description 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.
Title Concrete CMS before 9.5.3 is vulnerable to Stored XSS in the YouTube block (vWidth/vHeight)
Weaknesses CWE-79
References
Metrics cvssV4_0

{'score': 7.3, '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'}


Projects

Sign in to view the affected projects.

cve-icon MITRE

Status: PUBLISHED

Assigner: ConcreteCMS

Published:

Updated: 2026-09-15T13:44:30.063Z

Reserved: 2026-08-27T18:18:39.738Z

Link: CVE-2026-81900

cve-icon Vulnrichment

Updated: 2026-09-15T13:44:26.026Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-09-14T23:18:48.333

Modified: 2026-09-15T14:40:24.370

Link: CVE-2026-81900

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-15T10:15:17Z

Weaknesses