Firefox 150 turns its PDF viewer into a real PDF editor

With Firefox’s latest version 150 update for Windows, macOS, and Linux, Mozilla has introduced few genuinely new features but some noteworthy improvements. The split view is easier to use, the built-in PDF viewer is increasingly evolving into a PDF editor, and the developers have once again fixed a host of vulnerabilities.

Mozilla plans to release Firefox 151 in four weeks on May 19th, 2026.

What’s new in Firefox 150?

The split-screen feature introduced in Firefox 149 has been improved. You can now right-click on any link and select “Open link in split view,” and you can also swap the two halves of a split window.

The built-in PDF viewer/editor can now also reorder PDF documents and copy, paste, delete, or export pages. You can also copy and save images contained within PDFs. The ability to merge multiple PDF documents into a single file is expected to follow soon.

Firefox’s translation feature, which operates locally without cloud services and thus respects your privacy, can now do more than just translate the content of web pages you visit. If you visit about:translations in the address bar, you can translate any text (similar to how Google Search has done it for years).

The new profile management is now also available on Windows 10. This allows you to separate work and personal browsing, including bookmarks and passwords. On Windows 10 and 11, you can now also back up your profiles locally.

Firefox’s free VPN, which was introduced with Firefox 149 and has some limits, will be expanded with Firefox 151. It’ll eventually have a choice of locations: USA, Canada, Germany, the UK, or France. Currently, it’s always set to USA. Firefox for Android will also receive the VPN feature, although the exact date is not yet confirmed.

Security fixes in Firefox 150

In Mozilla’s Security Advisory 2026-30, the company lists 41 fixed security vulnerabilities. Around a third of the vulnerabilities are classified as high risk. These include several use-after-free vulnerabilities, for example in the JavaScript Engine and the HTML renderer. A further 18 vulnerabilities are classified as medium risk.

The last three entries in the Security Advisory list an unspecified number of internally discovered issues, grouped under CVE numbers CVE-2026-6784, CVE-2026-6785, and CVE-2026-6786. These problematic memory access errors are also classified as high risk. Some of them also affect Firefox ESR and Thunderbird.

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 Mozilla browser updates

In addition to Firefox 150, ESR versions 140.10.0 and 115.35.0 are also now available, although the latter is only available for Windows 7 and 8.1 and macOS 10.12 to 10.14.

In the ESR versions, Mozilla’s developers have fixed the aforementioned vulnerabilities that were already present in the legacy code of these browser generations, of which Firefox 140.10 contains at least 25 fixes and Firefox 115.35 at least 10 fixes. Firefox ESR 115 will continue to receive security updates until August 2026.

Thunderbird 150 and 140.10.0esr are also due to be released shortly. In these, the developers have likewise fixed dozens of security vulnerabilities inherited from its Firefox base.