WPJAM Basic <= 7.1 - Unauthenticated Privilege Escalation to 'data[args][role]' Parameter

The WPJAM Basic plugin for WordPress is vulnerable to Privilege Escalation in versions up to, and including, 7.1 This is due to the WPJAM_User_Signup::signup() function unpacking attacker-supplied `data[args]` from the AJAX POST body and merging it via PHP array union into the payload passed to WPJAM_User::create(), whose internal whitelist (wpjam_pick) explicitly preserves the `role` key before it is handed to wp_insert_user(). The endpoint is registered as wp_ajax_nopriv_{provider}-signup with a nonce that is emitted on the public login page. This makes it possible for unauthenticated attackers to elevate their privileges to Administrator by creating a new user with an attacker-chosen role, provided a social-login provider is registered and open registration is enabled.