Senior Software Engineer, Firefox Security - Mozilla

About Mozilla

Mozilla Corporation is the non-profit-backed technology company shaping the internet for the better. We make pioneering brands like Firefox, the privacy-minded web browser. Wholly owned by the non-profit 501(c) Mozilla Foundation, we 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 features: Implement, test, and ship cutting-edge security and hardening features for enterprise users that strengthen Firefox's overall security posture.
• Advance Firefox's security architecture: Drive improvements across multiple operating systems by building privilege isolation, moving trust boundaries, and improving core security mechanisms (cryptographic protocols, WebPKI, and security-sensitive web APIs).
• Contribute to security initiatives: Collaborate across teams to investigate security issues, identify root causes, and deliver robust, maintainable fixes.
• Improve reliability and performance: Diagnose and resolve stability, correctness, performance, and memory usage issues in a complex, multithreaded native environment.

What You'll Bring

• Systems programming & security expertise: 3+ years of experience in low-level software engineering, strong proficiency in C and/or C++, and a solid understanding of security fundamentals.
• Debugging & problem-solving: Demonstrated experience diagnosing issues in multithreaded, cross-platform native applications, including memory and performance optimization.
• Web platform knowledge: Familiarity with web technologies (HTML, CSS, JavaScript) and interest or experience in Rust.
• Collaboration: Experience working effectively within large multi-language codebases and distributed teams with clear written and verbal communication.

What You'll Get

• Performance-based bonus plans
• Generous retirement contributions with 100% immediate vesting
• Quarterly all-company wellness days and a quarterly well-being stipend
• One-time home office stipend
• Annual professional development budget
• Paid parental leave
• Country-specific holidays plus a day off on your birthday
• Employee referral bonus program and comprehensive health/life coverage