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ZDNET’s key takeaways
- Firefox 150 enhances split view, tab sharing, and other features.
- The latest version also fixes 271 security flaws.
- Anthropic’s Claude Mythos Preview AI model found some of the flaws.
Keeping your web browser updated can be a hassle. But typically, you want to snag the latest updates as they introduce new features and fix security holes. That’s certainly the case with the newest update to Firefox.
Released on Tuesday, Firefox 150 enhances a variety of must-have features, including split view, tab management, language translations, and the built-in PDF editor. But even more critically, the new version patches a whopping 271 security bugs, thanks to some help from AI.
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First, let’s look at the new and improved features.
Split View enhancements
Introduced to Firefox in March, Split View lets you view two web pages side-by-side in the same window, an option that had already been available in Chrome and Microsoft Edge. You can then compare the two pages and work with each one separately.
With Firefox 150, you can now right-click on any link on a page and open it in split view to see it alongside your current page. When in Split View mode, you’re also able to search your open tabs and reverse the order of the two pages.
Better tab sharing
You’ve always been able to share single pages in Firefox with another person or device. Now, you can share multiple tabbed pages in one shot. Just select the tabs you wish to share and right-click on any of them. Select Share from the menu and then click the command to copy X number of links. When you paste the links into other apps, both the page title and URL are included.
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This sounds like a useful feature if only it worked. In version 150, when I right-click multiple tabs, there is no Share command, unlike when I right-click a single tab. I contacted Mozilla to find out why this isn’t working as described.
Real-time translations
Need to translate a piece of text into a different language? You can now do that easily enough in Firefox. Type the phrase “about:translations” in the address field. You’re then taken to a translation page similar to Google Translate. Here, you can copy and paste the text you want translated. Select the source language or let the tool automatically detect it. Select the target language. The translation then appears.
PDF editing
Beyond just displaying a PDF you find online or load from your PC, Firefox will now let you edit it. Using the built-in PDF editor, you’re able to reorder, copy, paste, delete, and even export individual pages from a PDF.
To try this, open a PDF in Firefox and click the Manage pages icon in the upper left. You’ll then see thumbnails of all the pages in the file. Here, you can select individual pages to delete them, as well as copy or cut them to paste them elsewhere. You can also move pages by dragging and dropping them, and export individual pages as separate files. When done, you can save the modified PDF.
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To update Firefox on the desktop, click the three-lined icon at the top, click Help, and select About Firefox. The browser will automatically download and install the latest update if necessary. Restart Firefox and you’re set.
Security fixes
That brings us to the security patches. Firefox 150 includes fixes for 271 security vulnerabilities. However, only slightly more than 40 of these were severe or critical enough to be recorded as CVEs (Common Vulnerabilities and Exposures).
Most of the 271 bugs were rated as low or medium severity or otherwise didn’t merit status as a public CVE. Collectively, though, they still represent a significant number compared with the dozens of vulnerabilities typically addressed by past Firefox updates.
How did the Firefox team learn of so many security flaws in the browser? Thank AI.
To help them uncover underlying flaws in Firefox, the team turned to an early version of Anthropic’s Claude Mythos Preview, as revealed in a Mozilla blog post. Since February, the folks at Mozilla have been using frontier AI models to root out latent security holes in the browser. Previously, they used Anthropic’s Opus 4.6 model to scan Firefox version 148, leading to fixes for 22 security bugs.
Three of the vulnerabilities were specifically credited to Anthropic’s Claude AI. These were CVE-2026-6746, CVE-2026-6757, and CVE-2026-6758. Among them, the first was rated as high severity, while the other two were rated as medium. However, Claude apparently played a role in the discovery of all 271 vulnerabilities.
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“As part of our continued collaboration with Anthropic, we had the opportunity to apply an early version of Claude Mythos Preview to Firefox,” Mozilla said in its blog post. “This week’s release of Firefox 150 includes fixes for 271 vulnerabilities identified during this initial evaluation.”
Typically, actual humans seek out security flaws in products like Firefox. But even with different researchers and bug hunters using advanced tools, that process can take time and work. These early frontier AI models seem able to handle such a task as — or almost as — effectively but much faster.
In its blog post, Mozilla said that it hasn’t seen any bugs that couldn’t have been found by an elite human researcher. Score one for human beings. But on the flip side, the company also acknowledged that the Claude model has been able to uncover any category or level of vulnerability that humans can identify, meaning nothing has gotten past the AI so far.
Other major tech players such as Apple, Google, and Microsoft are also working with Claude Mythos as part of an initiative called Project Glasswing. Despite being in the preliminary states, this use of AI as a bug catcher does seem promising.
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But, yes, there’s always a but. Though Anthropic has purposely avoided releasing Claude Mythos publicly, there’s always a chance the bad guys could get their hands on it. That would certainly up their game to a new level.
“Claude Mythos being as good as an elite researcher is both good and bad,” Diana Kelley, chief information security officer at Noma Security, told ZDNET. “Defenders can accelerate testing and hardening, which is a real gain. At the same time, average attackers now have access to tools that deliver results that once required deep expertise, and they can operate at speeds 24/7.”