Vulnerability · Published May 7, 2026 · Assigned by GitHub_M

CVE-2026-41661Admidio: Reflected XSS in msg_window.php via Square Bracket to HTML Tag Conversion

Medium 6.1

In plain English

A medium-severity cross-site scripting in admidio from Admidio. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 8% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)6.1Medium

Exploit odds (30 days)0.2%top 92.3% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

Admidio is an open-source user management solution. Prior to version 5.0.9, an unauthenticated attacker can execute arbitrary JavaScript in any Admidio user's browser through a reflected XSS in system/msg_window.php. The endpoint passes user input through htmlspecialchars(), which does not encode square brackets. A subsequent call to Language::prepareTextPlaceholders() converts those brackets into HTML angle brackets, producing executable markup. This issue has been patched in version 5.0.9.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Packagist	admidio/admidio	5.0.9	GHSA-gq27-fc8w-vcmp

Affected products (as reported)

Vendor	Product	Versions
Admidio	admidio	< 5.0.9

Weakness: CWE-79 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

References

https://github.com/Admidio/admidio/security/advisories/GHSA-gq27-fc8w-vcmp x_refsource_CONFIRM
https://github.com/Admidio/admidio/releases/tag/v5.0.9 x_refsource_MISC