Modern Events Calendar (Lite & Pro) < 7.37.0 - Subscriber+ SQLi via mec_attendees AJAX Action

The Modern Events Calendar Lite WordPress plugin before 7.37.0, Modern Event Calendar Pro WordPress plugin before 7.37.0 do not sanitise and escape a parameter before using it in a SQL statement, which allows authenticated users with Subscriber-level access and above to append additional SQL queries into already existing queries and extract sensitive data from the database.