As announced in September, Chrome will soon mark non-secure pages containing password and credit card input fields as Not Secure in the URL bar.
This document is intended to aid Web Developers in updating their sites to avoid this warning.
Enable warnings
Warnings will be enabled by default for everyone in Chrome 56, slated for release in January 2017.
To test the upcoming user experience before that time, install the latest Google Chrome Canary build.
To configure Chrome to show the warning as it will appear in January 2017, open chrome://flags/#mark-non-secure-as and set the Mark non-secure origins as non-secure option to Display a verbose state when password or credit card fields are detected on an HTTP page. Then relaunch your browser.
You can see an example of the browser’s warning behavior on this page.
When the Not Secure state is shown, the DevTools console shows the message This page includes a password or credit card input in a non-secure context. A warning has been added to the URL bar.
Resolve warnings
To ensure that the Not Secure warning is not displayed for your pages, you must ensure that all forms containing <input type=password> elements and any inputs detected as credit card fields are present only on secure origins. This means that the top-level page must be HTTPS and, if the input is in an iframe, that iframe must also be served over HTTPS.
Warning: It is NOT sufficient to place an HTTPS iframe inside a HTTP page; the top-level page itself must be HTTPS as well.
If your site overlays an HTTPS login frame over HTTP pages...
...you will need to change the site to either use HTTPS for the entire site (ideal) or redirect the browser window to an HTTPS page containing the login form:
Long term - Use HTTPS everywhere
Eventually, Chrome will show a Not Secure warning for all pages served over HTTP, regardless of whether or not the page contains sensitive input fields. Even if you adopt one of the more targeted resolutions above, you should plan to migrate your site to use HTTPS for all pages.
Source: Lawrence, Eric. "Avoiding the Not Secure Warning in Chrome." developers.google.com,
https://developers.google.com/web/updates/2016/10/avoid-not-secure-warn. Accessed 9 October 2017.