mCatFilter <= 0.5.2 - Cross-Site Request Forgery via compute_post() Function
Strategic Overview
- Status
- Unpatched
- Affected Plugin
- mCatFilter
- Affected Version
<= 0.5.2- CVSS
- 4.3Medium
- Weakness type
- CWE-352 · Cross-Site Request Forgery (CSRF)
- CVE
CVE-2026-4139
At a glance
CVE-2026-4139 is a medium-severity Cross-Site Request Forgery (CSRF) vulnerability in the mCatFilter WordPress plugin, affecting versions <= 0.5.2. It carries a CVSS score of 4.3 (reachable over the network; low attack complexity). Exploitation requires no authentication. No fixed release has been reported yet; treat installations running this software as exposed. Disclosed April 2026, reported by afnaan.
Vulnerability Overview
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.
Technical Analysis
The vector marks this flaw as remotely reachable over the network, with low attack complexity — no special timing or configuration is needed, and no privileges on the target site.
CWE-352: Cross-Site Request Forgery (CSRF)
mCatFilter <= 0.5.2 carries this weakness at compute_post(), and reaching it takes a caller who can reach the endpoint. Cross-site request forgery abuses the fact that browsers attach a victim's cookies to any request, so a state-changing action that only checks who you are, not whether you meant to act, can be triggered from another site.
An attacker who gets a logged-in user to load a crafted page can perform that action as them, with the impact scaling to whatever the victim's role is allowed to do. No fixed build of this plugin is recorded for mCatFilter yet, so installs running <= 0.5.2 stay exposed until the vendor ships one.
Remediation
No known patch available. Please review the vulnerability's details in depth and employ mitigations based on your organization's risk tolerance. It may be best to uninstall the affected software and find a replacement.
How does WordSec protect against this?
The attempt arrives as an ordinary request to mCatFilter: WordSec's web application firewall inspects request payloads before WordPress loads them. No patched version is recorded yet, which is the case where a filtering layer matters most, because there is nothing to update to.
- Firewall
- Alerts
External References
Vulnerability data © Defiant, Inc., provided under the Wordfence Intelligence T&C