Firefox Application Security Team: Firefox Security & Privacy Newsletter 2026 Q1

Welcome to the Q1 2026 edition of the Firefox Security & Privacy Newsletter.

Security and privacy are foundational to , until the majority of our user population have received Firefox updates. If a link does not work for you, please accept this as a precaution for the safety of all Firefox users.

Firefox Product Security & Privacy

Collaboration with Anthropic: A few weeks ago, Anthropic’s Frontier Red Team shared the results of a new AI-assisted vulnerability detection approach. Using this method, we have identified more than a dozen confirmed security issues, each supported by reproducible test cases. Learn more in our blog: , to , all the way to the at ), leveling-up the built-in protection from online threats.

Stronger XSS Protection through the Sanitizer API: Starting with v148, Firefox was the first browser to add support for the , or tune in to the for certificates issued by Mozilla’s built-in root CAs. As publicly trusted CAs already meet this requirement, no significant impact to the broader web is expected.

Community Engagement

Bug Bounty Program Updates: As the threat landscape evolves, addressing the increasing volume of AI-assisted security bug reports, we’re evolving our security program alongside it. With continued advances in browser security architecture, our bug bounty program is refining its incentives to prioritize the highest-impact research and the most critical classes of vulnerabilities while focusing on novelty. Learn more in our blogpost: , to list all people who helped us find and fix security vulnerabilities in Q1 of 2026.

Web Security & Standards

Storage-Access Headers: Firefox 147 is shipping an extension of the Storage Access API to improve both web compatibility and parity with Chrome. These Storage Access headers allow web pages to opt out of storage isolation upfront and without the need to first load a document.

Going Forward

As a Firefox user, you automatically benefit from the security and privacy improvements described above through Firefox’s regular automatic updates. If you’re not using Firefox yet, you can download it to enjoy a fast, secure browsing experience—while supporting Mozilla’s mission of a healthy, safe, and accessible web for everyone.

We’d like to thank everyone who helps make Firefox and the open web more secure and privacy-respecting.

See you next time with the Q2 2026 report.

— The Firefox Security and Privacy Teams