The latest version of Firefox for Windows, macOS, Linux, and Android brings a number of improvements to privacy protection, the built-in PDF viewer/editor, and the VPN feature, plus fixes for over 30 security vulnerabilities. Updates are also available for the ESR versions.
What’s new in Firefox 151?
The free VPN feature that was introduced back in Firefox 149 now offers a choice of several virtual locations. Firefox’s VPN feature is currently available to users in the US, Canada, the UK, France, and Germany—and those very countries are now available as VPN locations. You’ll need a free Mozilla account to use the VPN, and you’ll get 50 GB of VPN traffic allowed per month. The location selection is gradually rolling out.
If you use Firefox private windows, you can now clear an entire session with one button click, no need to close the browser window. This will start a fresh private session with no history. There’s also improved tracking protection in Firefox 151, which Mozilla claims should reduce the number of users that advertisers can identify using standard fingerprinting techniques by 14 percent overall (reduced by up to 50 percent on macOS alone).
Mozilla
The revamped “New Tab” page offers more background images and is ready for new features that Mozilla plans to roll out in the lead up to the release of Firefox 152 on June 16th.
The built-in PDF viewer/editor has gained another feature: it can now merge multiple PDF files into a single document. The internal page for translating any text (//about:translations) is now also accessible via the menu under “More Tools.” Linux users can now also back up their Firefox profiles locally and restore them across platforms.
Security flaws fixed in Firefox 151
In Mozilla’s Security Advisory 2026-46 for Firefox 151, the company lists over 30 fixed security vulnerabilities, 28 of which were discovered and reported by external security researchers.
Mozilla classifies four of those 28 externally discovered security vulnerabilities as high risk, including a potential escape from the browser sandbox (CVE-2026-8945). A further 11 vulnerabilities are classified as medium risk, with the remainder as low risk. The last three entries in the Security Advisory summarize internally discovered vulnerabilities resulting from programming errors in memory management.
Tip: Whether you keep your browser up to date, you need proper antivirus protections if you want your PC to remain secure and private. Check out our picks for the best antivirus software for Windows as well as best VPN services to stay ahead of security problems.
Other browser updates
In addition to Firefox 151.0, the ESR versions 140.11.0 and 115.36.0 are also available. The latter is only available for Windows 7/8.1 and macOS 10.12 to 10.14. In the ESR versions, Mozilla’s developers have fixed those of the above-mentioned vulnerabilities that were already present in the code of those older browser generations: Firefox 140.11 contains at least 20 fixes and Firefox 115.35 has at least seven fixes. Firefox ESR 115 will continue to receive security updates until August 2026.
Thunderbird 151.0 and 140.11.0esr are also due to be released shortly. In these versions, the developers have likewise fixed dozens of security vulnerabilities inherited from Firefox.
