Senior Software Engineer, Firefox Security - Mozilla

Why Mozilla?

Mozilla Corporation is the non-profit-backed technology company that has shaped the internet for the better over the last 25 years. We make pioneering brands like Firefox, the privacy-minded web browser. Now, with more than 225 million people around the world using our products each month, we’re shaping the next 25 years of technology and helping to reclaim an internet built for people, not companies. Our work focuses on diverse areas including AI, social media, security, and more—all while staying focused on our core mission.

The Mozilla Corporation is wholly owned by the non-profit 501(c) Mozilla Foundation. This means we aren’t beholden to shareholders—only to our mission. Along with thousands of volunteer contributors and collaborators worldwide, Mozillians design, build, and distribute open-source software that enables people to enjoy the internet on their terms.

What You’ll Do

• Design, build, and implement security and hardening features: Design, implement, test, and ship cutting-edge security features that strengthen Firefox’s security posture for enterprise and everyday users.
• Advance Firefox’s security architecture: Drive improvements to Firefox’s core security posture across multiple operating systems by building privilege isolation, shifting trust boundaries, and hardening mechanisms including cryptographic protocols, WebPKI, and security-sensitive web APIs.
• Contribute to security initiatives: Work cross-functionally to investigate security issues, identify root causes, and ship robust, maintainable fixes.
• Improve browser reliability and performance: Diagnose and resolve issues affecting stability, correctness, performance, and memory usage in a complex, multithreaded environment.

What You’ll Bring

• Systems programming & security knowledge: 3+ years of experience in low-level software engineering, strong proficiency in C and/or C++, and a solid foundation in security fundamentals.
• Debugging & problem-solving skills: Proven experience diagnosing and resolving issues in multithreaded, cross-platform native applications, including memory and performance challenges.
• Web platform & modern systems experience: Familiarity with web technologies (HTML, CSS, JavaScript) and interest or experience in Rust; ability to navigate large, complex, multi-language codebases.
• Effective collaboration: Track record of thriving in distributed teams and communicating complex technical concepts clearly in writing and conversation.

What You’ll Get

• Generous performance-based bonus plans
• Generous retirement contributions with 100% immediate vesting
• Quarterly all-company wellness days
• Country-specific holidays plus your birthday off
• One-time home office stipend
• Annual professional development budget
• Quarterly well-being stipend
• Paid parental leave
• Employee referral bonus program
• Comprehensive health and life benefits (varies by country)