I have a quick tip: there's an issue with the Github pages SSL certificate. Apparently it's an easy fix: https://stackoverflow.com/a/42177720/359774

Thank God, I've tried to solve this for quite some time now. You're the man!!

Check out https://zulipchat.com - it's a cool mix between instant messaging and a forum.

This looks great, thanks for the hint!

HackerOne has a list of publicly disclosed bugs here https://hackerone.com/hacktivity/popular

Also, you might want to take a look at https://exploit-exercises.com

Hope these help, good luck with the interview!