Mozilla Firefox 40 was released yesterday and available for upgrade in Ubuntu 15.10, Ubuntu 15.04, Ubuntu 14.04 and Ubuntu 12.04 repositories.

Release highlights according to the official release note:

• Support for Windows 10
• Added protection against unwanted software downloads
• User can receive suggested tiles in the new tab page based on categories Firefox matches to browsing history (en-US only).
• Hello allows adding a link to conversations to provide context on what the conversation will be about
• New style for add-on manager based on the in-content preferences style
• Improved scrolling, graphics, and video playback performance with off main thread compositing (GNU/Linux only)
• Graphic blocklist mechanism improved: Firefox version ranges can be specified, limiting the number of devices blocked
• Add-on extensions that are not signed by Mozilla will display a warning
• NPAPI Plug-in performance improved via asynchronous initialization
• Smoother animation and scrolling with hardware vsync (Windows only)
• JPEG images use less memory when scaled and can be painted faster
• Sub-resources can no longer request HTTP authentication, thus protecting users from inadvertently disclosing login data
• IndexedDB transactions are now non-durable by default
• Implemented AudioBufferSourceNode.detune to modulate playback rate in cents, a logarithmic unit of measure used for musical intervals
• Improved Performance tools in the developer tools: Waterfall view, Call Tree view and a Flame Chart view
• New rules view tooltip in the Inspector to tweak CSS Filter values
• Console API messages from SharedWorker and ServiceWorker are now displayed in web console
• New page ruler highlighting tool that displays lightweight horizontal and vertical rules on a page
• Inspector now searches across all content frames in a page
• Fix that Kannada text does not display properly in built-in pdf viewer
• security fixes.

How to upgrade:

The packages has been made into Ubuntu updates and security repositories. Just search for and launch Software Updater and install the updates after checking for updates: