LearnPress <= 4.4.4 - Authenticated (Administrator+) SQL Injection via 'orderby' Parameter

The LearnPress plugin for WordPress is vulnerable to SQL Injection via the 'orderby' parameter of the export_order_csv AJAX action in versions up to, and including, 4.4.4. This is due to insufficient escaping on the user supplied parameter and lack of sufficient preparation on the existing SQL query in the LP_Order::handle_params_query_list_orders() and DataBase::execute() functions — only the literal values 'date' and 'title' are normalized, while any other attacker-controlled string is assigned directly to the filter's order_by property and concatenated into the ORDER BY clause without $wpdb->prepare() or an identifier whitelist. This makes it possible for authenticated attackers, with administrator-level access and above, to append additional SQL queries into already existing queries that can be used to extract sensitive information from the database.