Get the Whitepaper called On WebSockets in Penetration Testing. It goes into detail discussing the vulnerability attack surface with WebSockets and the complications involved for penetration testing.
You can download it from the following link: https://packetstormsecurity.com/files/download/121432/AC07815487.pdf
Source: https://packetstormsecurity.com/files/121432/WebSockets-Penetration-Testing.html