14 DAY TRIAL // Firefox 23 Aurora isn't out yet, but it should become available any time now. Mozilla is already talking about it and the major new feature, a new Mixed Content Blocker UI.
Firefox already had the ability to block unencrypted content served through encrypted pages.
This is important because the web today is incredibly interdependent. Any given page will load scripts and resources for many other sites and domains, sometimes dozens of them.
While the page itself may be served via an encrypted HTTPS connection, the resources may be loaded as plain text via HTTP.
This creates a false sense of security, as users believe they are protected since they're using a HTTPS connection, but active content, i.e. scripts, loaded via HTTP could be used to track their actions or, worse, alter the page they're on.
So, starting with Firefox 23, active content will be blocked, though passive mixed content, i.e. images, will still be loaded.
Firefox already supported mixed content blocking, but without the UI to control it, the feature wasn't enabled by default. Firefox 23 changes that, and mixed content blocking is turned on by default and users are now notified when content is blocked by the browser.
The tricky part was how to keep users informed without annoying them. A popup or a notification every time a user visited a page with mixed content would quickly wear people out.
Instead, when Firefox blocks unencrypted content a shield icon will be displayed in the address bar. If the user clicks on it, more info will be displayed, as well as the option to turn off the block for that page permanently.
If users do decide to allow unencrypted content to load, a yellow warning sign will be displayed instead of the lock icon. When only passive content will be let through, the regular globe icon will be displayed instead of the lock icon.