Firefox 151 Enhances Privacy, Introduces PDF Merging, and Patches Over 30 Vulnerabilities
Overview of Firefox 151
The latest iteration of Mozilla’s browser, Firefox 151, is now rolling out across Windows, macOS, Linux, and Android. This update brings a host of enhancements focused on user privacy, an upgraded PDF editor, and a more versatile VPN feature. Additionally, Mozilla has addressed more than 30 security flaws in this release, making it a critical update for all users. Extended Support Releases (ESR) versions 140.11.0 and 115.36.0 have also been patched accordingly.
What’s New in Firefox 151
VPN Now Offers Multiple Virtual Locations
The complimentary VPN service introduced in Firefox 149 has been expanded. Users can now select from several virtual locations instead of a single default server. Currently, this feature is accessible to individuals in the United States, Canada, the United Kingdom, France, and Germany—exactly the same countries now available as selectable VPN endpoints. To use the VPN, you need a free Mozilla account, which grants 50 GB of monthly traffic. The location picker is being deployed gradually, so some users may see it later than others.
Easier Private Session Management
Private browsing receives a significant usability boost. You can now clear an entire private session with a single click, eliminating the need to close the entire browser window. This action starts a fresh private session with no history retained. Combined with this, Mozilla claims improved tracking protection that reduces the number of users identifiable via standard fingerprinting by 14% overall—and by up to 50% on macOS alone.
Built-in PDF Viewer Gains File Merging
The browser’s native PDF viewer and editor now support merging multiple PDF files into a single document. This feature streamlines document management without requiring third-party tools. Additionally, the translation tool, previously accessible only through the about:translations internal page, can now be reached via the More Tools menu, making it more convenient for everyday use.
Refreshed New Tab Page
The redesigned New Tab page offers a broader selection of background images and is prepared for upcoming features that Mozilla plans to introduce before Firefox 152’s release on June 16. This update sets the stage for a more customizable start page experience.
Linux Profile Backup and Cross-Platform Restore
Linux users can now back up their Firefox profiles locally and restore them across different operating systems. This capability simplifies migration or recovery of browsing data, such as bookmarks, passwords, and settings.
Security Flaws Fixed in Firefox 151
According to Mozilla’s Security Advisory 2026-46, over 30 vulnerabilities have been resolved. Of these, 28 were discovered and reported by external security researchers, reflecting Mozilla’s commitment to community-driven security.
Four of the externally reported flaws are classified as high risk, including a potential sandbox escape tracked as CVE-2026-8945. Eleven medium-risk vulnerabilities were patched, and the remaining externally found issues are considered low risk. The advisory also notes three internally discovered vulnerabilities stemming from programming errors in memory management, which have been rectified.
Staying Secure Beyond the Browser
While keeping your browser up to date is essential, it’s only one piece of the security puzzle. For comprehensive protection, consider using reputable antivirus software and a VPN service. We recommend reviewing our guides to the best antivirus software for Windows and top VPN services to strengthen your online defenses.
Other Browser Updates
In addition to Firefox 151, Mozilla has released ESR versions 140.11.0 and 115.36.0. The latter is exclusively for Windows 7/8.1 and macOS 10.12 to 10.14. These ESR updates include fixes for the vulnerabilities present in their respective codebases, ensuring legacy users remain protected.