X (Formerly Twitter): cookie injection allow dos attack to periscope.tv

Description: i find in periscope.tv a parameter "createuser" allow to inject "loginissignup" cookie, when tested with crlf payload get response "HTTP/1.1 504 GATEWAYTIMEOUT" Link Vulnerable: https://www.periscope.tv/i/twitter/login?createuser=payload&csrf=yourcsrftoken Steps To Reproduce: 1. go t...