CVE-2026-11366 is an improper authentication vulnerability (CWE-287) in the MonsterInsights WordPress plugin versions prior to 11.1.0. The plugin fails to properly validate the signature on one of its unauthenticated AJAX actions when it is not connected to Google Analytics. Specifically, the HMAC signing key used for signature validation is empty, allowing unauthenticated attackers to forge a valid signature. This flaw enables attackers to overwrite configuration values of the plugin, which disrupts the server-side analytics functionality when operating in Manual GA4 mode.

An attacker can exploit this vulnerability without authentication to modify MonsterInsights plugin configuration values. This can disrupt the plugin's server-side analytics in Manual GA4 mode, potentially affecting data accuracy and analytics reporting. There is no indication from the data that this leads to broader system compromise or data leakage beyond the analytics disruption.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is released, users should monitor vendor communications for updates. No vendor advisory or patch links are currently available, so no official remediation or temporary fixes can be recommended at this time.