Welcome. Here is a proof of concept in what I’m calling NAT Pinning (“hacking gibsons” was already taken). The idea is an attacker lures a victim to a web page. The web page forces the user’s router or firewall, unbeknownst to them, to port forward any port number back to the user’s machine. If the user had FTP/ssh/etc open but it was blocked from the router, it can now be forwarded for anyone to access (read: attack) from the outside world. No XSS or CSRF required.