In the past, Mozilla has planned for the Firefox browser to display an insecure password warning for HTTP websites/pages that has login form, but not enabled by default in Firefox release or beta versions till now. The company has turned on the feature by default in Firefox 50 beta, and the target milestone for this was set to Firefox 51.
With this, when a user visits a non-secure HTTP page that has a password field, Firefox browser shows the gray lock icon with a red strike-through, when the user clicks on it Control Center shows this information: ‘Connection is Not secure Logins entered on this page could be compromised’ .
While this warning icon can be easily ignored or may not seen by the user, Mozilla is doing its bit to alert user that login information over insecure connection can be easily stolen by eavesdroppers and attackers. Google Chrome to do this as well from version 56 onwards, eventually Chrome will mark HTTP pages as non-secure.
Firefox 52: Contextual Warning for Insecure Login Field
How to Prevent Chrome and Firefox Browsers From Storing Passwords?