Vulnerability-Lookup

CVE-2026-41661 (GCVE-0-2026-41661)

Vulnerability from cvelistv5 – Published: 2026-05-07 02:59 – Updated: 2026-05-07 14:58

Title

Admidio: Reflected XSS in msg_window.php via Square Bracket to HTML Tag Conversion

Summary

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.

Severity ?

6.1 (Medium)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

CWE

CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Assigner

GitHub_M

References

2 references

URL	Tags
https://github.com/Admidio/admidio/security/advis…	x_refsource_CONFIRM
https://github.com/Admidio/admidio/releases/tag/v5.0.9	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
Admidio	admidio	Affected: < 5.0.9

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-41661

Vulnerability from fkie_nvd - Published: 2026-05-07 04:16 - Updated: 2026-05-07 16:16

Severity ?

6.1 (Medium) - CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/Admidio/admidio/releases/tag/v5.0.9
	security-advisories@github.com	https://github.com/Admidio/admidio/security/advisories/GHSA-gq27-fc8w-vcmp
	134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/Admidio/admidio/security/advisories/GHSA-gq27-fc8w-vcmp

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "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\u0027s 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."
    }
  ],
  "id": "CVE-2026-41661",
  "lastModified": "2026-05-07T16:16:20.270",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 6.1,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "LOW",
          "integrityImpact": "LOW",
          "privilegesRequired": "NONE",
          "scope": "CHANGED",
          "userInteraction": "REQUIRED",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 2.8,
        "impactScore": 2.7,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-05-07T04:16:29.920",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/Admidio/admidio/releases/tag/v5.0.9"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/Admidio/admidio/security/advisories/GHSA-gq27-fc8w-vcmp"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "url": "https://github.com/Admidio/admidio/security/advisories/GHSA-gq27-fc8w-vcmp"
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}

GHSA-GQ27-FC8W-VCMP

Vulnerability from github – Published: 2026-04-29 21:51 – Updated: 2026-05-08 20:13

Summary

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

Details

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

Severity ?

6.1 (Medium)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 5.0.8"
      },
      "package": {
        "ecosystem": "Packagist",
        "name": "admidio/admidio"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "5.0.9"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-41661"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-29T21:51:13Z",
    "nvd_published_at": "2026-05-07T04:16:29Z",
    "severity": "MODERATE"
  },
  "details": "## Summary\n\nAn unauthenticated attacker can execute arbitrary JavaScript in any Admidio user\u0027s 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.\n\n## Details\n\nThe `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:\n\n```php\n// system/msg_window.php:146\n$messageText = $gL10n-\u003eget($messageId, array(htmlspecialchars($messageVar1)));\n```\n\n`htmlspecialchars()` encodes `\u003c`, `\u003e`, `\u0026`, `\"`, and `\u0027` but leaves `[` and `]` untouched. The `Language::get()` method calls `Language::prepareTextPlaceholders()`, which performs a character-level translation:\n\n```php\n// src/Infrastructure/Language.php:497\n$text = strtr($text, \u0027[]\u0027, \u0027\u003c\u003e\u0027);\n```\n\nThis 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 `\u003cscript\u003ealert(document.domain)\u003c/script\u003e` after placeholder preparation.\n\nThe application sets no Content-Security-Policy headers, so inline scripts execute without restriction.\n\n## Proof of Concept\n\nVisit the following URL on any Admidio installation (no authentication required):\n\n```\nhttps://\u003cadmidio-host\u003e/system/msg_window.php?message_id=INS_INSTALLATION_VERSION\u0026message_var1=%5Bscript%5Dalert(document.domain)%5B/script%5D\n```\n\nThe server responds with an HTML page containing:\n\n```html\nInstallation version \u003cscript\u003ealert(document.domain)\u003c/script\u003e\n```\n\nThe JavaScript executes in the context of the Admidio origin, displaying the current domain in an alert dialog.\n\n## Impact\n\nAn 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.\n\n## Recommended Fix\n\nApply 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()`.\n\n---\n*Found by [aisafe.io](https://aisafe.io)*",
  "id": "GHSA-gq27-fc8w-vcmp",
  "modified": "2026-05-08T20:13:52Z",
  "published": "2026-04-29T21:51:13Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/Admidio/admidio/security/advisories/GHSA-gq27-fc8w-vcmp"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-41661"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/Admidio/admidio"
    },
    {
      "type": "WEB",
      "url": "https://github.com/Admidio/admidio/releases/tag/v5.0.9"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Admidio vulnerable to reflected XSS in msg_window.php via Square Bracket to HTML Tag Conversion"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

CVE-2026-41661 (GCVE-0-2026-41661)

FKIE_CVE-2026-41661

GHSA-GQ27-FC8W-VCMP

Summary

Details

Proof of Concept

Impact

Recommended Fix

Tags

Sightings

Nomenclature