Handsome Testimonials & Reviews < 2.1.1 - Authenticated (Subscriber+) SQL Injection

The hndtst_action_instance_callback AJAX call of the Handsome Testimonials & Reviews WordPress plugin before 2.1.1, available to any authenticated users, does not sanitise, validate or escape the hndtst_previewShortcodeInstanceId POST parameter before using it in a SQL statement, leading to an SQL Injection issue.