Few days ago Mozilla announced the official release of Firefox 139, accompanied by the classic security updates for the extended support versions: Firefox 115.24.0 and 128.11.0.
Firefox 139 fixes 14 vulnerabilities, eight of which are related to memory management errors that could allow the execution of malicious code. Of particular note is vulnerability CVE-2025-5262, rated critical, caused by a double free in the libvpx encoder, which affects the VP8 and VP9 formats and can be exploited via WebRTC.
Main new features of Firefox 139
One of the main new features of Firefox 139 is the ability to customize the new tab page with a background image or a solid color. Although this feature It is not yet activated by default for all users., is being rolled out gradually. If you'd like to enable it manually, you can do so from the Firefox Labs section under about:settings#experimental. New default background images have also been added, including a space-inspired category called "Celestial."
Another new feature in Firefox 139 is the experimental function de AI-powered link preview. By holding down the Alt+Shift keys and hover over a link, a pop-up window with information is displayed Contextual: title, image, and a summary of the content. This feature relies on an extensive language model hosted locally on the user's system and can also be enabled from Firefox Labs. 
Moreover, the Firefox Translator is now also able to translate the content of internal pages extensions, accessible via URLs like moz-extension://. This reinforces the translator's usefulness in contexts where it didn't work before.
Performance improvements and changes to migration from Chrome
EData loading performance has improved significantly thanks to the optimization of the HTTP/3 protocol, especially in situations where a connection is resumed (QUIC 0-RTT) or working with high latency and bandwidth channels.
Moreover, because Chrome has started encrypting data confidential in Windows, Firefox can no longer directly import passwords or payment methods.To migrate, users must manually export their passwords from Chrome in CSV format and load them into Firefox.
Goodbye to Fakespot and Pocket
With the announcement by Mozillaat the end of two integrated servicess: Review Checker (Fakespot) will be disabled on June 10, while Pocket will be discontinued on July 8.
In addition to this, with this version, The Temporary object is enabled by default. This AModern PI allows manipulation of dates and times accurately, either in time-zone-independent representations or even as a timestamp. It also offers support for arithmetic operations and format conversion.
Notable changes for power users and developers include:
- Reduced accuracy of timers in worker-intensive environments.
- More comprehensive on-page searches: blocks now expand automatically that contain matches.
- New options for local text search with hidden elements thanks to the hidden="until-found" attribute.
- The window.getSelection().toString() method now correctly serializes selected text in forms.
- WebAuthn now supports largeBlob and credProps extensions to associate additional data with user credentials.
- The HTMLDialogElement API includes the requestClose() method, which allows you to cancel the closing of a dialog box if the cancel event is intercepted.
- Improvements to the behavior of elements with contenteditable and designMode, making them more consistent with Chrome.
- In the developer tools, network filters are preserved across sessions, and the JavaScript debugger now displays a clearer layout at the stop point.
Specific improvements in Android
The mobile version for Android adds handy features like bookmark sorting, an improved interface for download management, more options for the news service and initial support for the modern JetPack Compose framework.
Interested in knowing more about it, you can consult the release notes in the following link
How to install Firefox on Linux?
If you are already a Firefox user, you should know that you can easily update to the latest version accessing the configuration menu. Those with automatic updates enabled need not worry as they will receive the new version without manual intervention.
Alternatively, if you prefer not to wait for the automatic update, you can do it manually by going to Menu > Help > About Firefox. This will open a window showing the installed version and, if the feature is enabled, it will check for available updates.
For Ubuntu, Linux Mint and other derivatives users from Ubuntu, too It is possible to update Firefox through the official PPATo do this, open a terminal and enter the following commands:
sudo add-apt-repository ppa:ubuntu-mozilla-security/ppa -y sudo apt-get update sudo apt install firefox
Another available installation option is via Flatpak. To use this method, you need to have Flatpak support on your system. Once enabled, you can install Firefox by running the following command in the terminal:
flatpak install flathub org.mozilla.firefox
As for those who already have the browser installed, it is enough to execute the following command to not only update Firefox, but also all its applications that are in Flatpak format:
flatpack update
In the case of those who prefer the use of Snap, the installation of the browser can be done by typing the following command:
sudo snap install firefox
And to update the applications that we have installed in Snap format, just type the following in the terminal:
sudo snap refresh