A while ago I experimented with adding stuff to the version.bind field in bind. Just updated it:

mike@glue:~$ dig +short chaos txt version.bind @198.211.125.252

"<iframe width='420' height='315' src='//www.youtube.com/embed/dQw4w9WgXcQ?autoplay=1' frameborder='0' allowfullscreen></iframe>"

I put this in my named.conf:

version "<iframe width='420' height='315' src='//www.youtube.com/embed/dQw4w9WgXcQ?autoplay=1' frameborder='0' allowfullscreen></iframe>";

This site is vulnerable:

http://dnscheck.pingdom.com/?domain=grepular.com

Although takes a minute before it kicks in. I did report it to them at the time, but never got a response.