The Speedup Optimization plugin for WordPress is vulnerable to Missing Authorization in all versions up to and including 1.5.9. The speedup01_ajax_enabled() function, which handles the wp_ajax_speedup01_enabled AJAX action, does not perform any capability check via current_user_can() and also lacks nonce verification. This is in contrast to other AJAX handlers in the same plugin (e.g., speedup01_ajax_install_iox and speedup01_ajax_delete_cache_file) which properly check for install_plugins and manage_options capabilities respectively. This makes it possible for authenticated attackers, with Subscriber-level access and above, to enable or disable the site's optimization module by sending a POST request to admin-ajax.