Groundhogg <= 4.5.5 - Authenticated (Sales Rep+) SQL Injection via 'query[select]' Parameter

The Groundhogg — CRM, Newsletters, and Marketing Automation plugin for WordPress is vulnerable to generic SQL Injection via 'query[select]' Parameter in all versions up to, and including, 4.5.5 due to insufficient escaping on the user supplied parameter and lack of sufficient preparation on the existing SQL query. This makes it possible for authenticated attackers, with Sales Representative-level access and above, to append additional SQL queries into already existing queries that can be used to extract sensitive information from the database. The sanitized Contact_Query code path can be bypassed by supplying an invalid filter type (e.g., query[filters][0][0][type]=invalid_filter_nonexistent), causing a FilterException to be caught and execution to fall through to the unsanitized Legacy_Contact_Query path.