Firefox 146 adds Windows backup, improved privacy, and security fixes

What’s new in Firefox 146?

Firefox 146 provides Windows users with a backup feature for all important data. Its main purpose is to make it easier to switch from Windows 10 to Windows 11. Without synchronization, which would require you to log in, you can back up your browser data locally or to OneDrive so that it’s available on your new Windows 11 PC. (This backup feature is rolling out gradually, so isn’t available on all systems yet.)

For the weather report on Firefox’s homepage, it makes sense for the browser to know your location. However, this isn’t always desirable, as privacy is pretty important to Firefox users. For users in the EU, the location is now only determined with the user’s consent (opt-in). This new improvement is also being introduced gradually.

You can now also activate experimental features in Firefox without having to participate in the transmission of telemetry data.

Security fixes in Firefox 146

Mozilla lists at least 13 eliminated security vulnerabilities in the 2025-92 Security Advisory. Five of the externally reported vulnerabilities are categorized as high risk, with two of them relating to errors in the JavaScript JIT compiler. A use-after-free (UAF) vulnerability has also been fixed in the WebRTC component.

The last two entries in the Security Advisory concern an unspecified number of internally discovered flaws, which are lumped under CVE-2025-14332 and CVE-2025-14333. They’re only considered medium risk. Attacks on these vulnerabilities are not yet known.

Further browser updates

In addition to Firefox 146.0, ESR versions 140.6.0 and 115.31.0 are also now available, although the latter is only available for Windows 7 and 8.1 and macOS 10.12 to 10.14. In these versions, Mozilla has fixed the above-mentioned vulnerabilities that are already present in the code of these browser generations, some of which were quite old.

The latest Tor Browser 15.0.3 is based on Firefox ESR 140.6 and comes with the NoScript 13.5.2 extension. For users of Windows 7 and 8.1 and macOS 10.12 to 10.14 only, Tor Browser 13.5.26 is based on Firefox ESR 115.31, including NoScript 13.5.2. The Tor Project now hosts NoScript for its browser itself, as seen by the fact that the NoScript version has the suffix “.1984” (currently 13.5.2.1984). Otherwise, it’s identical to the version on Firefox’s Add-On Store.

Thunderbird 146.0, which can now handle Exchange, and 140.6.0esr have also been released. The developers have fixed one or two security vulnerabilities that the mail app inherited from Firefox.