Input validation vulnerability in Appointment Booking Calendar — Simply Schedule Appointments Booking Plugin 1.6.6.20

The Simply Schedule Appointments plugin for WordPress has a security issue that makes it vulnerable to a type of hacking called Reflected Cross-Site Scripting. This can happen in versions 1.6.6.20 and below because the plugin does not properly clean up or protect the information that is put into it. As a result, people who are not logged in can add harmful code to pages that will run if someone clicks on a certain link.