UsersWP < 1.2.59 - Authenticated (Subscriber+) Restricted Usermeta Modification via 'htmlvar' Parameter

Description

The UsersWP – Front-end login form, User Registration, User Profile & Members Directory plugin for WordPress is vulnerable to Improper Access Control in all versions up to, and including, 1.2.58 This is due to insufficient field-level permission validation in the upload_file_remove() AJAX handler where the $htmlvar parameter is not validated against a whitelist of allowed fields or checked against the field's for_admin_use property. This makes it possible for authenticated attackers, with subscriber-level access and above, to clear or reset any restricted usermeta column for their own user record, including fields marked as "For admin use only", bypassing intended field-level access restrictions.