ExactMetrics <= 9.1.2 - Authenticated (Editor+) Arbitrary Plugin Installation/Activation via exactmetrics_connect_process

The ExactMetrics – Google Analytics Dashboard for WordPress (Website Stats Plugin) plugin for WordPress is vulnerable to unauthorized arbitrary plugin installation and activation in all versions up to, and including, 9.1.2. This is due to the reports page exposing the 'onboarding_key' transient to any user with the 'exactmetrics_view_dashboard' capability. This key is the sole authorization gate for the '/wp-json/exactmetrics/v1/onboarding/connect-url' REST endpoint, which returns a one-time hash (OTH) token. This OTH token is then the only credential checked by the 'exactmetrics_connect_process' AJAX endpoint — which has no capability check, no nonce verification, and accepts an arbitrary plugin ZIP URL via the file parameter for installation and activation. This makes it possible for authenticated attackers, with Editor-level access and above granted the report viewing permission, to install and activate arbitrary plugins from attacker-controlled URLs, leading to Remote Code Execution.