The Perfect Survey WordPress plugin before 1.5.2 does not validate and escape the question_id GET parameter before using it in a SQL statement in the get_question AJAX action, allowing unauthenticated users to perform SQL injection.
https://wpscan.com/vulnerability/c1620905-7c31-4e62-80f5-1d9635be11ad
http://packetstormsecurity.com/files/166072/WordPress-Perfect-Survey-1.5.1-SQL-Injection.html