The slickquiz plugin through 1.3.7.1 for WordPress allows SQL Injection by Subscriber users, as demonstrated by a /wp-admin/admin.php?page=slickquiz-scores&id= or /wp-admin/admin.php?page=slickquiz-edit&id= or /wp-admin/admin.php?page=slickquiz-preview&id= URI.
https://wordpress.org/plugins/slickquiz/#developers
http://packetstormsecurity.com/files/154440/WordPress-SlickQuiz-1.3.7.1-SQL-Injection.html