Senior Firefox Security Engineer — Remote

Thunderbird; España; Remote; EUR 66,000 - 88,000; Full time

Benefits offered by this job

Performance bonus

Retirement contributions

Wellness days

Birthday holiday

Home office stipend

Professional development budget

Well-being stipend

Parental leave

Employee referral bonus

Other benefits

Job summary

Mozilla Corporation is seeking a Senior Software Engineer, Firefox Security, to design and implement enterprise security features that strengthen Firefox’s security posture across multiple operating systems. You will drive improvements to core security mechanisms and collaborate with teams to investigate issues and deliver robust fixes.

The role emphasizes memory management, performance, and multithreaded reliability, with opportunities to contribute to cryptographic protocols, WebPKI, and

Qualifications

• 3+ years of experience in low‑level software engineering with strong security fundamentals.
• Experience diagnosing and resolving issues in multithreaded, cross‑platform native applications including memory and performance challenges.
• Familiarity with web technologies (HTML, CSS, JavaScript) and interest or experience in Rust; ability to work within large, multi‑language codebases.
• Effective collaboration and communication across distributed teams.

Responsibilities

• Design, build and implement security features to strengthen Firefox’s security posture.
• Advance Firefox’s security architecture across multiple operating systems and strengthen core security mechanisms.
• Investigate security issues, identify root causes, and deliver robust, maintainable fixes.
• Diagnose and resolve issues affecting stability, performance, and memory usage in a complex, multithreaded environment.

Skills

Systems programming

Security knowledge

Debugging and problem-solving

Communication

Tools

C/C++

Rust

Web technologies (HTML/CSS/JS)

Job description

Mozilla Corporation is seeking a Senior Software Engineer, Firefox Security, to design and implement enterprise security features that strengthen Firefox’s security posture across multiple operating systems. You will drive improvements to core security mechanisms and collaborate with teams to investigate issues and deliver robust fixes.

The role emphasizes memory management, performance, and multithreaded reliability, with opportunities to contribute to cryptographic protocols, WebPKI, and