Firefox 46.0 was released on April 26, 2016 to the stable channel. The new version of the web browser is offered as an update or as a separate download from the Mozilla website.

Firefox releases run in sync which means that all channels of the web browser are updated at the same time and moved up a version in the process.

Apart from Firefox 46 Stable, this means that Firefox Beta 47, Firefox Developer Edition 48, and Firefox Nightly 49 have also been released.

The Extended Support Release version of Firefox is updated to 38.8 and 45.1, with 38.8 being the last major release of the 38.x series.

Executive Summary

Firefox add-on signing is enforced in Firefox 46 on the Stable or Beta channels but not mandatory. Mozilla plans to make it mandatory with the release of Firefox 47. This means that it is still possible to flip a switch in Stable and Beta versions of Firefox to install and run unsigned add-ons.

Multi-process Firefox is not enabled in version 46 Stable.

Firefox for Android dropped support for Android 3.x devices.

Async Pan Zoom (APZ) is not enabled in Firefox 46.

Netflix works in Firefox 46 without plugins as it uses a native CDM now if supported.

Firefox 46 download and update

Firefox 46 has been released by Mozilla. The new version is distributed via the web browser's update mechanics but also available as a download from the Mozilla website.

Note: if you are reading this on April 26, it may not be available for you yet. Download links and update servers will deliver the new version of Firefox on that day, and it may take a while before everything is updated.

If you are using automatic updates in Firefox, you may speed up the update process by checking for the update manually.

This is done in the following way:

Use the Alt-key on the computer keyboard to display the menu of the web browser. Select Help > About Firefox from the menu that opens up. Firefox displays the current version of the browser and checks if updates are available. If the update to Firefox 46 is found, it can be downloaded and installed automatically.

The following links provide lead to the official download site on the Mozilla website. You may download and install new versions by downloading them from Mozilla and running the installer afterwards.

Firefox 46 Changes

Firefox 46 is a rather uneventful release as it ships with just a couple of feature additions, and most of those are not even visible to the user.

Use Content Decryption Module as a fallback to decode unencrypted H.264 and AAC media where available.

If a Content Decryption Module (CDM) is installed in Firefox, it will be used to decode media that is unencrypted if the default method does not work correctly.

You can load about:addons, and switch to the plugins section on the page that opens up, to find out if Content Decryption Modules are installed in Firefox.

These are only available on Windows Vista and newer versions of Windows, and on the Mac OS platform.

W^X JIT-code enabled in Firefox

W^X or Write XOR Execute, is a security policy for memory pages that defines them as either writable or executable, but not both.

Basically, what it does is improve the browser's security against attacks targeting Firefox's Just in Time compiler and is also beneficial against memory corruption.

You can read more about this in here.

Other changes

Support for blocking DNS requests when .,onion domains are accessed. Handled by the preference network.dns.blockDotOnion .

WebRTC fixes to improve performance and stability. This includes support for simulcast and support for several other features. You can check out the full release notes on Mozilla's Wiki site.

GTK3 integration (GNU/Linux only) which brings along with it several improvements including better input device support or HiDPI widget drawing.

Developer Changes

Dominators and Allocations view in the Developer Tools.

Implementation of CSS Grids has been updated.

Truckload of JavaScript related changes including ES6 improvements but also removal of non-standard functions.

WEBGL_compressed_texture_esr extension is now implemented. To use it, set the preference webgl.enable-draft-extensions to true .

to . Permissions API has been enabled by default.

Launch responsive mode from the Style Editor @media sidebar

Firefox for Android

Firefox for the desktop and for Android share code but there are usually some changes that affect only the Android version of the browser.

Firefox will request permissions at runtime instead of installation time (Android 6.0+)

Firefox on devices running Android 6.x will request permissions during runtime and not during installation anymore.

Firefox for Android will check whether permissions have been given to it already when functionality requires additional permissions, and if that is not the case, ask for the permissions to execute the desired activity.

Cached pages are loaded when the device is offline

Firefox for Android will use the browser cache when the device is offline and pages are requested that are cached.

Include default domains for inline autocompletion

When you type in Firefox's address bar, suggestions are displayed as you type. Firefox uses previously visited domains for that, but since there are none when you start using the browser after initial installation, it uses a fallback now.

Basically, what it does is grab top sites using Alexa (or similar services), and provide those as an initial list for inline autocompletion.

Other Firefox 46 for Android changes

Notifications about tabs opened in the background now list the URLs. Firefox for Android allows you to open tabs in the background, and the notifications that it displays then include the web address now.

Clearer homescreen shortcut icons.

History and Bookmarks items added to menu.

Top Sites panel now lists popular sites by default.

Removed support for Firefox Sync 1.1 in favor of Firefox Account.

Dropped support for Android Honeycomb (version 3).

Prevent the installation of unsigned add-ons.

Security updates / fixes

Security updates are disclosed after the official release. We update the article as soon as they become available.

MFSA 2016-48 Firefox Health Reports could accept events from untrusted domains

MFSA 2016-47 Write to invalid HashMap entry through JavaScript.watch()

MFSA 2016-46 Elevation of privilege with chrome.tabs.update API in web extensions

MFSA 2016-45 CSP not applied to pages sent with multipart/x-mixed-replace

MFSA 2016-44 Buffer overflow in libstagefright with CENC offsets

MFSA 2016-43 Disclosure of user actions through JavaScript with motion and orientation sensors

MFSA 2016-42 Use-after-free and buffer overflow in Service Workers

MFSA 2016-41 Content provider permission bypass allows malicious application to access data

MFSA 2016-40 Privilege escalation through file deletion by Maintenance Service updater

MFSA 2016-39 Miscellaneous memory safety hazards (rv:46.0 / rv:45.1 / rv:38.8)

Firefox 46.0.1

Firefox 46.0.1 is a minor update that has been released on May 3, 2016 to the stable channel. It fixes the following issues:

Fix page loading issues caused by antivirus software (1268922)

Fix search plugin issues for locales (1246949)

Fixed an add-on signing certificate expiration bug (1267318)

Server worker update issue (1267733)

Build issue when jit is enabled (1266366)

Limit sync registration updates (1262312)

Additional information / sources

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