ElementCamp <= 2.3.6 - Authenticated (Author+) SQL Injection via 'meta_query[compare]' Parameter

Description

The ElementCamp plugin for WordPress is vulnerable to time-based SQL Injection via the 'meta_query[compare]' parameter in the 'tcg_select2_search_post' AJAX action in all versions up to, and including, 2.3.6. This is due to the user-supplied compare value being placed as an SQL operator in the query without validation against an allowlist of comparison operators. The value is passed through esc_sql(), but since the payload operates as an operator (not inside quotes), esc_sql() has no effect on payloads that don't contain quote characters. This makes it possible for authenticated attackers, with Author-level access and above, to append additional SQL queries into already existing queries that can be used to extract sensitive information from the database.