Zen Browser 1.23.3b was released on October 16, 2026, featuring an upgrade to Firefox 158.0, which brings numerous critical security fixes from Mozilla's MFSA2026-106 advisory. In addition to security enhancements, the update introduces new features such as a command-line flag for launching specific Spaces, improved PDF accessibility on Linux and macOS, and better scrolling on high-resolution displays. While Zen Browser is positioned as a free and open-source alternative to Arc Browser, it does not support Widevine DRM, which affects streaming from services like Netflix and HBO Max. The rapid development cycle has allowed Zen to quickly incorporate these updates, enhancing both functionality and security for its users

Zen Browser 1.23.3b Ships with Firefox 158 Security Fixes

Zen Browser 1.23.3b shipped on October 16, 2026, as a maintenance build that upgrades its engine to Firefox 158.0, inheriting Mozilla's high-impact MFSA2026-106 advisory with dozens of critical security fixes. Alongside the security upgrades it adds practical touches: a new --space command-line flag, more accessible PDFs on Linux and macOS, and smoother scrolling on high-resolution displays. As a free, open-source Firefox fork pitched as the open alternative to Arc Browser, it rides Zen's unusually rapid weekly release cycle that has steadily hardened the newly introduced Library hub.

Zen Browser 1.23.3b Ships with Firefox 158 Security Fixes @ Linux Compatible