Firefox 136 Update: Vertical Tabs, Improved Security, and More
The latest Firefox 136 update has arrived, bringing a range of exciting new features and improvements to Mozilla’s popular web browser. The standout addition is vertical tabs, now featured in a newly designed sidebar that helps manage numerous open tabs with ease. This new interface provides a clearer overview, making it easier to navigate when you have many tabs open.
But the update isn’t just about convenience—it also comes with enhanced security. The 2025-14 Security Advisory highlights at least 15 fixed vulnerabilities, five of which carry a high-risk rating. Notable among them is CVE-2025-1930, which could allow attackers to break out of Firefox’s sandbox on Windows. Additionally, Mozilla has patched several high-risk vulnerabilities that could potentially lead to code injection and execution. Users of Firefox ESR and Tor Browser will benefit from these security fixes as well.
Another feature users will appreciate is the sidebar that can now store bookmarks, history, and give you access to an AI chatbot, as well as tabs from other synced devices. The sidebar is customizable—allowing you to move it from left to right, and even store browser extensions there if developers add support. To enable the sidebar, navigate to Settings > General, and activate the Show Sidebar option.
The vertical tabs feature, which is now available in the sidebar, moves your usual browser tabs to the side, stacking them one below another. This allows for more tab visibility, especially when you have many open at once. You can toggle this feature via the sidebar customization settings.
Additionally, Firefox 136 introduces HTTPS-First by default, which forces Firefox to attempt an encrypted HTTPS connection whenever possible. If that fails, it will fall back to the traditional, unencrypted HTTP protocol.
Mozilla also made waves in February by updating its Terms of Use to clarify its data collection practices. While some users voiced concerns, these changes are largely due to legal regulations in certain U.S. states, and the updates should not cause alarm.
Updates for Firefox ESR and Tor Browser
Mozilla has also issued updates for Firefox ESR and Tor Browser. These updates fix security issues and vulnerabilities in Firefox ESR 128 and 115, with 10 vulnerabilities patched in version 128.8.0 and five in 115.21.0. Tor Browser 14.0.7, based on Firefox ESR 128, is also available for download. Additionally, Tor Browser 13.5.13 is now available for Windows 7, 8.1, macOS 10.13, and 10.14.
Mozilla has confirmed that Firefox ESR 115 will be supported until at least September 2025, with further decisions to be made in August 2025. The future of Tor Browser 13.5.x, based on Firefox ESR 115, remains uncertain, and whether further support will be provided is still under discussion.
