User Profile Builder 3.16.4 - Unauthenticated Authentication Bypass
The User Profile Builder plugin for WordPress version 3.16.4 is vulnerable to an authentication bypass via type confusion. Profile Builder's automatic-login-after-registration handler passes the return value of wp_insert_user() through absint() before testing it with is_wp_error(), so the error check runs against the already-coerced integer. A registration submitted with a 61-70 character username passes the plugin's own validation but is rejected by WordPress core, because the user_login column is VARCHAR(60), and wp_insert_user() returns a WP_Error object. absint() coerces that object to the integer 1, is_wp_error(1) is false, and the plugin binds a transient-backed autologin nonce to user ID 1. Consuming that nonce calls wp_set_auth_cookie(1) and logs the unauthenticated attacker in as the site's Administrator.