The source is every test server, doesnt matter if public or under NDA..... But the NDA ones got the most gamebreaking bugs that are fixed before showing the public.
very sensitive stuff goes on the UAT server. we test all kinds of new....things. we socialise, we laugh, we cry, we plan for worlddomination by means of human sacrifices to our dark lord Satan and...ah crap...plz dont put me on the kill list...
I guess im not breaking NDA when i say, the most typed sentence on the UAT is something like "Man, can't wait to see that on live" followed by "Jeah, me neither" This doesn't come out of nowhere but hopefully you will see yourself today if that's true or not