CVE-2026-81894
Published:September 15, 2026
Updated:September 22, 2026
Concrete CMS 9.5.2 and below is vulnerable to stored DOM-based Cross-site Scripting (XSS) via the Gallery block's per-image Caption field because the bundled Magnific Popup lightbox script (concrete/js/features/imagery/frontend.js) re-parses the attribute-decoded caption as HTML through jQuery's .append() in titleSrc instead of inserting it as text. A user with permission to edit a page containing a Gallery block can store a caption that executes in the browser of any visitor who opens that image's lightbox. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 8.5 with vector CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N. Thanks Yonatan Drori (Tenzai) for reporting.
Affected Packages
https://github.com/concretecms/concretecms.git (GITHUB):
Affected version(s) >=9.0.0RC4 <9.5.3Fix Suggestion:
Update to version 9.5.3concrete5/core (PHP):
Affected version(s) >=9.0.0RC4 <9.5.3Fix Suggestion:
Update to version 9.5.3Related Resources (1)
Do you need more information?
Contact UsCVSS v4
Base Score:
8.5
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
HIGH
User Interaction
PASSIVE
Vulnerable System Confidentiality
HIGH
Vulnerable System Integrity
HIGH
Vulnerable System Availability
HIGH
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
6.8
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
HIGH
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
HIGH
Weakness Type (CWE)
EPSS
Base Score:
0.14