Tutor LMS <= 4.0.5 - Unauthenticated Remote Code Execution via 'template' and 'data' POST Parameters

The Tutor LMS – eLearning and online course solution plugin for WordPress is vulnerable to Remote Code Execution limited to zero-argument function invocation in all versions up to, and including, 4.0.5 via the tutor_course_filter_ajax AJAX action. This is due to missing authorization on the handler combined with unsanitized array keys being passed to extract() inside tutor_load_template(), allowing attacker-controlled POST data to overwrite the local $template variable and, in the resulting templates/single-content-loader.php template, the $method_map and $context variables invoked at $method_map[$context](). This makes it possible for unauthenticated attackers to call an arbitrary zero-argument PHP function server-side and, via WordPress core edit_user(), to create a persistent subscriber-level account from request parameters.