Reflected XSS due to vulnerable version of sockjs

## Summary: There is reflected XSS on *.simperium.com. The bug exists due to a vulnerable version of sockjs library. ## Platform(s) Affected: simperium.com js.simperium.com ## Steps To Reproduce: 1. Visit https://simperium.com/sock/1/0/0/0/htmlfile?c=alert('XSS')// 2. You will see an alert message because of executed JS ## Impact XSS may be used by an attacker to perform a lot of things, for example, to steal user session