Mozilla has rolled out Firefox 147, introducing several enhancements and fixes. Among them are upgrades to Safe Browsing version 5 for better privacy, a refined picture-in-picture video feature, and resolutions for multiple security issues.
The next version, Firefox 148, is scheduled for release on February 24, approximately six weeks ahead. This timeline raises ongoing discussions about whether Mozilla will prolong support for Firefox 115 on legacy systems like Windows 7 and 8, as well as macOS versions 10.12 through 10.14.
The longstanding picture-in-picture video functionality now triggers automatically when the containing tab moves out of focus. It deactivates once the tab returns to the active state. This mirrors actions seen in platforms such as YouTube.
Developers at Mozilla have also equalized video rendering speeds on AMD graphics hardware to align with levels achieved on Intel and Nvidia cards.
Integration of Google's Safe Browsing v5 significantly cuts down on remote server checks. Instead, the browser keeps an up-to-date onsite database of identified malicious or risky sites. It verifies incoming URLs against this list without transmitting them to external services.
According to Mozilla's Security Advisory 2026-01 for Firefox 147, at least 16 flaws have been addressed. Six externally disclosed issues are rated as high severity, with four involving escapes from the browser's isolation environment. Such exploits might allow arbitrary code insertion and execution at the system level, though no real-world incidents have been reported.
The advisory's final sections cover an undisclosed count of flaws found by Mozilla's team, grouped under CVE-2026-0891 and CVE-2026-0892. These impact Firefox ESR and Thunderbird alike, with varying severity levels from high to medium.
Alongside the standard Firefox 147.0, updated ESR builds include 140.7.0 and 115.32.0, the last of which supports only Windows 7, 8.1, and macOS 10.12 to 10.14. All incorporate patches for the vulnerabilities affecting their shared codebase.
Tor Browser's newest iteration, 15.0.4, draws from Firefox ESR 140.7 and bundles the NoScript 13.5.7 add-on. An older variant, 13.5.27 based on ESR 115.32 with the same NoScript, remains accessible for Windows 7, 8.1, and macOS 10.12 to 10.14 users.
The Tor Project now maintains its own NoScript distribution, identifiable by the '.1984' extension in versions like 13.5.7.1984—a nod to George Orwell. Functionally, it matches the edition available via Mozilla's add-on repository.
Releases of Thunderbird 147.0 and 140.7.0esr have arrived as well, patching a couple of security weaknesses carried over from Firefox's framework.
This piece originated on affiliate site PC-WELT, adapted and translated from its German version. Freelance contributor Frank Ziemann has covered news and reviews for PC-WELT since 2005, specializing in IT security topics like malware, antivirus solutions, and online technologies.