Firefox and Chrome have patched more than 200 security flaws combined, so update both as soon as possible.

Meta description: Firefox 159 and Chrome updates fix 219 security bugs, including 108 high-severity Firefox flaws and four critical Chrome issues, so update browsers now.

Tags: Firefox 159, Chrome update, browser security, use-after-free, Smart Window

Featured image: Abstract technology style browser security shield, no real people, no company logos, no text.

Background: Browser Security Stays the First Line of Defense

Firefox and Chrome are where people read, buy, bank, and work, so browser security becomes a routine but urgent control point. ZDNET has framed this exposure as significant, noting that half of all cyberattacks start in the browser. That context matters because Mozilla and Google are not releasing minor cosmetic versions this time. They are shipping patch sets that close hundreds of defects, including issues that can let an attacker crash a browser or run malicious code inside protected areas.

Development: Firefox 159 Moves First, Then Chrome Follows

This week, Mozilla updated Firefox to version 159 for Windows, Android, MacOS, and Linux. The release includes fixes for 167 security bugs. Of those, 108 are rated high severity, while the rest are considered moderate or low. Almost 100 are use-after-free vulnerabilities, a memory management flaw that an attacker could exploit to crash the browser or trigger malicious code. Several bugs also refer to Firefox’s Sandbox, meaning hackers could break through the browser’s protected Sandbox area to execute malicious code.

Firefox 159 also adds features beyond security. In Firefox for the Mac, sharing a page now displays the built-in MacOS share picker, showing a preview along with recent contacts and apps such as AirDrop and Messages. Users can access Firefox’s passwords tool in the sidebar by making the sidebar visible, clicking the Sidebar button on the Address bar, then clicking the key icon. The AI-powered Smart Window can now watch specific web pages for changes and send a notification when a page is updated. To use it, enable Smart Window from the Firefox icon in the upper right, go to the website, type `/watch` in the chat window, fill out the form, and click Create Task.

Chrome then received version 56.0.8078.73/.74 for Windows and Mac and version 156.0.8078.73 for Linux. This update patches 52 security bugs. Four are rated critical, while 46 are rated high. The four severe issues point to a memory corruption problem, and like some Firefox bugs, they reference Chrome’s Sandbox. An attacker exploiting one of these vulnerabilities could bypass Chrome’s protected Sandbox area to run malicious code. Several Chrome bugs also point to use-after-free issues that could crash the browser or allow malicious code to be installed.

Latest Progress: AI Helps Surface a Combined 219 Flaws

Taken together, Firefox and Chrome close 219 security bugs in this cycle, more than 200 combined. The severity mix is important: Firefox carries the larger volume, with 108 high-severity fixes and almost 100 use-after-free-related flaws, while Chrome carries a smaller but sharper set, including four critical memory corruption and Sandbox-related problems. The pattern suggests that browser attack surface remains concentrated in memory handling and isolation boundaries.

Both browsers also show a growing role for AI in vulnerability discovery. In its advisory, Mozilla cited Amy Burnett, a security research and analyst at OpenAI, for uncovering many of the bugs. In its blog post, Google attributed the discovery of several flaws to Anthropic’s Claude and a few to OpenAI. ZDNET also disclosed that Ziff Davis, ZDNET’s parent company, filed an April 2025 lawsuit against OpenAI, alleging it infringed Ziff Davis copyrights in training and operating its AI systems.

For update paths, Firefox users can open the browser, click the three-line icon at the upper right, move to Help and Report, select About Firefox, install the latest update, and restart the browser. Chrome users can click the three-dot icon at the top, move to Help, select About Google Chrome, allow the update to download if prompted, and restart the browser.

Current Stage: Patch Rollout and AI-Assisted Disclosure Are Now the Norm

The current stage is a rapid patch cycle across Firefox and Chrome, with both vendors moving from vulnerability reporting to shipped fixes. Firefox 159 combines 167 fixes with new sharing, password sidebar, and page-watch features, while Chrome’s release addresses 52 bugs, including four critical issues. What to watch next is how often AI-assisted reports feed into browser advisories, and whether memory corruption and Sandbox bypass bugs continue to dominate the next security releases.