Webpage login and password problem

Hello all. I have been playing around with the ethernet shield on my Uno.
All is OK, and I lifted some login+password code from the following thread (Zoomcats code)

It works, but the problem is it displays the username and password in the URL at the top of the page as well, so its not exactly hard to hack!

My code is basically the same as in the thread (and I have tried some other too), but when I get in I can post it if need be.
Is there any way of preventing it posting the returned values to the address bar?

Or… does anyone know of a better way of achieving a login+password

Thanks

Use POST instead of GET for your form method: https://www.w3schools.com/tags/ref_httpmethods.asp