How severe is GHSA-gq27-fc8w-vcmp?

GHSA-gq27-fc8w-vcmp has a CVSS score of 6.1/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by GHSA-gq27-fc8w-vcmp?

GHSA-gq27-fc8w-vcmp affects the following packages: admidio/admidio (Packagist). Ecosystems affected: Packagist.

How do I fix GHSA-gq27-fc8w-vcmp?

Update admidio/admidio to 5.0.9 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-gq27-fc8w-vcmp is resolved across your whole dependency graph.

How do I detect GHSA-gq27-fc8w-vcmp in my Packagist dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for admidio/admidio. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate GHSA-gq27-fc8w-vcmp if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against GHSA-gq27-fc8w-vcmp?

O3 pinpoints whether GHSA-gq27-fc8w-vcmp is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is GHSA-gq27-fc8w-vcmp actively exploited in the wild?

No public exploit code has been indexed for GHSA-gq27-fc8w-vcmp yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

When was GHSA-gq27-fc8w-vcmp published, and has it been updated?

GHSA-gq27-fc8w-vcmp was published on April 29, 2026 and was last updated on May 8, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐘 Packagist

GHSA-gq27-fc8w-vcmp

MEDIUM

GHSA-gq27-fc8w-vcmp is a medium-severity (CVSS 6.1) vulnerability in admidio/admidio. O3 Security confirms whether GHSA-gq27-fc8w-vcmp is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.

Admidio vulnerable to reflected XSS in msg_window.php via Square Bracket to HTML Tag Conversion

Also known asCVE-2026-41661

Published

Apr 29, 2026

Updated

May 8, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Real-World Exposure

1 pkg affected

🐘admidio/admidio

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.

Description

Summary

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.

Details

The msg_window.php endpoint accepts message_id and message_var1 as GET parameters. At line 146, the code passes message_var1 through htmlspecialchars() before inserting it into the language string as a placeholder:

// system/msg_window.php:146
$messageText = $gL10n->get($messageId, array(htmlspecialchars($messageVar1)));

htmlspecialchars() encodes <, >, &, ", and ' but leaves [ and ] untouched. The Language::get() method calls Language::prepareTextPlaceholders(), which performs a character-level translation:

// src/Infrastructure/Language.php:497
$text = strtr($text, '[]', '<>');

This converts all square brackets in the output string, including those from user input, into angle brackets. An attacker submits [script]alert(document.domain)[/script], which survives htmlspecialchars() unchanged, then becomes <script>alert(document.domain)</script> after placeholder preparation.

The application sets no Content-Security-Policy headers, so inline scripts execute without restriction.

Proof of Concept

Visit the following URL on any Admidio installation (no authentication required):

https://<admidio-host>/system/msg_window.php?message_id=INS_INSTALLATION_VERSION&message_var1=%5Bscript%5Dalert(document.domain)%5B/script%5D

The server responds with an HTML page containing:

Installation version <script>alert(document.domain)</script>

The JavaScript executes in the context of the Admidio origin, displaying the current domain in an alert dialog.

Impact

An attacker crafts a malicious URL and sends it to any Admidio user. When the victim clicks the link, attacker-controlled JavaScript runs in their browser session. The attacker can steal session cookies, perform administrative operations on behalf of the victim, or redirect the victim to phishing pages. The endpoint requires no authentication.

Recommended Fix

Apply output encoding after Language::prepareTextPlaceholders() runs, or stop translating square brackets that originate from user-supplied placeholder values. A targeted fix: escape [ and ] in user input before passing it into Language::get().

Found by aisafe.io

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`admidio/admidio`	all versions	5.0.9

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for admidio/admidio. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update admidio/admidio to 5.0.9 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-gq27-fc8w-vcmp is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-gq27-fc8w-vcmp is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to GHSA-gq27-fc8w-vcmp. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

## Summary 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. ## Details The `msg_window.php` endpoint accepts `message_id` and `message_var1` as GET parameters. At line 146, the code passes `message_var1` through `htmlspecialchars()` before inserting it into the lan

O3 Security · Impact-Aware SCA

Is GHSA-gq27-fc8w-vcmp in your dependencies?

O3 detects GHSA-gq27-fc8w-vcmp across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

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