A few days ago, Mozilla released a new version of Firefox for Windows and Linux. Version 46 comes with security fixes and a couple of new features under the hood. But the most notable change is for Linux users: they got the first official version built using the GTK+ 3 framework.
As you might be knowing, Mozilla was going to remove the option xpinstall.signatures.required from about:config in Firefox 44. Once this option would have been removed, the user would have been unable to bypass the digital signature enforcement for add-ons. Mozilla has changed their mind and decided to keep the option till the Firefox 46 release.