Flex Store Users <= 1.1.0 - Unauthenticated Privilege Escalation

The Flex Store Users plugin for WordPress is vulnerable to Privilege Escalation in all versions up to, and including, 1.1.0. This is due to the 'fsUserHandle::signup' and the 'fsSellerRole::add_role_seller' functions not restricting what user roles a user can register with. This makes it possible for unauthenticated attackers to supply the 'administrator' role during registration and gain administrator access to the site. Note: The vulnerability can be exploited with the 'fs_type' parameter if the Flex Store Seller plugin is also activated.