The 6Storage Rentals plugin for WordPress is vulnerable to authentication bypass in versions up to, and including, 2.27.0. This is due to the six_storage_create_wp_user() AJAX handler being registered on wp_ajax_nopriv_six_storage_create_wp_user without any nonce, capability, credential, or ownership verification, while calling wp_set_current_user() and wp_set_auth_cookie() for any WordPress user resolved by the attacker-supplied email address. This makes it possible for unauthenticated attackers to log in as any existing WordPress user, including administrators, by submitting that user's email address.