CVE-2026-81918 Concrete CMS below 9.5.3 is vulnerable to Stored XSS via the Date Format field in the Page Attribute Display block

Medium 4.8 Published 11 Sep 2026 Updated 14 Sep 2026

An attacker with page editing permissions can inject malicious scripts via the Date Format field, executing code in visitors' browsers.

Exploited in the wild: Not known
Login needed: An administrator
Attackable: Over the internet
Victim action needed: A user has to click or open something
Fix: None listed

What is CVE-2026-81918?

CVE-2026-81918 is a medium-severity cross-site scripting vulnerability in Concretecms Concrete Cms, published on 11 Sep 2026. An attacker needs administrator access to exploit it, and only if a user opens a file or follows a link.

Official description

Concrete CMS below 9.5.3 is vulnerable to Stored XSS via the Date Format field in the Page Attribute Display block. A user with edit_page_contents permissions could store a payload which executes in the browser of any visitor who viewed a page where the block was configured to display a date-type attribute. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 4.8 with vector CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N. Thanks Oriol Ortiz for reporting.

Weakness: CWE-79

Which versions are affected by CVE-2026-81918?

It affects 1 product.

Products include Concretecms Concrete Cms.

How do I fix CVE-2026-81918?

No fix has been published for CVE-2026-81918 yet. Limit exposure of the affected software until one is available.

Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.

Is CVE-2026-81918 being exploited?

There is no known exploitation of CVE-2026-81918 in the wild and no public exploit code.

All Concretecms Concrete Cms vulnerabilities

Sources

Also known as GHSA-j987-77r9-4hgr.