You can easily fix this yourself.
1) Change your server's user & password.
2) Keep only the config file, delete the other files and replace them with clean Xenforo files to be safe.
3 Revert the database to a working backup prior to being hacked.
4) Update your Xenforo installation to the...
There seems to be an issue with this add-on and @Matt C. . 's gamer profiles. When you click on "Gamer Cards" within a profile and you have a vanity URL this is what happens:
Any chance of this getting fixed in an updated version? Thanks!