ARMember Premium <= 7.3.1 - Unauthenticated SQL Injection via 'order' Parameter

The ARMember Premium plugin for WordPress is vulnerable to SQL Injection via the 'order' parameter of the 'arm_directory_paging_action' AJAX action in all versions up to, and including, 7.3.1. This is due to insufficient escaping on the user-supplied 'order' and 'orderby' parameters and the lack of sufficient preparation on the existing SQL query in the `arm_get_directory_members()` function. This makes it possible for unauthenticated attackers to append additional SQL queries into already existing queries that can be used to extract sensitive information from the database.