Mozilla officially released the Firefox 58.0 web browser today, the second major update to the new “Quantum” series, which brings new features and improvements.

Firefox 58 “Quantum” is the first release of the web browser to incorporate security fixes to mitigate the Meltdown and Spectre timing attacks by default for new installations. The Firefox 57 “Quantum” series includes these patches only with the 57.0.4 point release.

Among other new features implemented in Firefox 58, we can mention a new two-tiered compiler and streaming compilation support to make WebAssembly even faster, enablement of the WebVR technology by default for Mac OS X users, and credit card info support in the autofill feature.

Mozilla also optimized the loading of web pages by implementing a method to cache JavaScript internal representation and improved web page rendering speed for Windows system with the Off-Main-Thread Painting function. Other than that, Firefox 58 includes support for the Nepali (ne-NP) locale.

The Firefox Screenshots component introduced with Firefox 57 has been updated to allow users to copy and paste screenshots directly to their clipboard, as well as to be compatible with the Private Browsing mode, and Mozilla finally fixed a bug that would make fonts installed in a non-standard directory to appear blank on Linux-based systems.

“With this release, we’re building on the great foundation provided by our all-new Firefox Quantum browser. We’re optimizing the performance gains we released in 57 by improving the way we render graphics and cache JavaScript. We also made functional and privacy improvements to Firefox Screenshots,” reads the release notes.

Mozilla also said that Firefox 58 adds a new warning message to alert users and website owners of any planned security changes to websites that are affected by the gradual distrust plan for the Symantec certificate authority. The PerformanceNavigationTiming API was implemented as well, along with PerformanceResourceTiming.workerStart for measuring service worker startup time.

User profiles created in Firefox 58 cannot be used in older versions

With the Firefox 58 release, Mozilla also makes it harder for users to downgrade as all user profiles created in Firefox 58 and future releases of the web browser cannot be used in a previous release, not even on Firefox 57 “Quantum.” Mozilla recommends users who want to downgrade to create a new profile instead.

However, some issues remain unresolved in Firefox 58 “Quantum,” as Mozilla informs Linux and Windows users that the web browser might crash occasionally on machines powered by Intel Broadwell-U processors using an old microcode firmware. The company urges users to update to the latest microcode version.

You can download Mozilla Firefox 58.0 for GNU/Linux, macOS, and Windows systems right now through our website. The Firefox 58 “Quantum” release is also available via OTA (Over-the-Air) updates for Windows and Mac users, which is the recommended method of upgrading to a new release.