Firefox 95 released today by Mozilla for Linux, macOS, and Windows. The release includes RLBox, a new security sandboxing technology. Mozilla researchers developed RLBox, in collaboration with the University of California San Diego and the University of Texas, to make it easy and efficient to isolate subcomponents by using WebAssembly to isolate potentially-buggy code. This serves to make Firefox more secure.
With the release of Firefox 95, Mozilla isolates five different modules — Graphite, Hunspell, Ogg, Expat, and Woff2 — and treats the modules as untrusted code. In doing so, if any of the isolated modules experiences a problem, it will not pose a threat to Firefox as a whole. You can read more details about RLBox on Mozilla’s Hacks blog.
Firefox 95 includes 14 security fixes, 7 of which have a High impact rating. Users should update Firefox as soon as possible.
Other New Features
In other related news, Firefox users now have the option to download the browser from the Microsoft Store on Windows 10 and Windows 11. To download Firefox for Windows from the Microsoft Store, follow these steps:
- Search Windows for Microsoft Store
- Select “Microsoft Store app” from the results
- Type Firefox in the search bar and press Enter
- Select “Mozilla Firefox” from the applications available
- Click Get to start the installation process

Also in this release, Mozilla reduced CPU usage on macOS in Firefox and WindowServer during event processing. They have also reduced the power usage of software decoded video on macOS, especially in fullscreen. This includes streaming sites such as Netflix and Amazon Prime Video.
Firefox users can now move the Picture-in-Picture toggle button to the opposite side of the video. Look for the new context menu option Move Picture-in-Picture Toggle to Left (Right) Side.
Finally, to better protect Firefox users against side-channel attacks such as Spectre, Site Isolation is now enabled for all Firefox 95 users.
References for December 7, 2021, release of Firefox Browser 95.0
- See What’s New: Firefox 95.0 Release Notes
- Firefox Latest Security Advisories
- US-CERT: Mozilla Releases Security Update for Firefox
- Download Firefox 95.0
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Henry Irvine, Contributing Technology Writer, translates more than a decade of internet technology experience in product and customer relationship management into practical help and how-to content. Look for him on Bay Area trails, music venues, or sausage shacks when he’s not writing. Don’t call him Hank if you see him. Seriously. Hank on Twitter