Senior Software Engineer, Firefox Security

at Mozilla Corporation

Team:Firefox Locations:Remote Spain, Remote Germany, Remote Sweden, Remote France, Remote UK, Remote Finland, Remote Belgium, Remote Netherlands

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. And we’re doing this while never losing our focus on our core mission – to make the internet better for people.

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

What you’ll do:

**Advance Firefox's security architecture and cryptography stack:**Contribute to improvements in Firefox's core security systems, with a focus on cryptographic protocols, WebPKI, and security-sensitive web APIs. Help implement and maintain security features that support the evolution of public key infrastructure on the web.
**Design and implement web platform security features:**Develop and ship web platform features in collaboration with teammates and the broader web community. Contribute to standards-based, secure, and interoperable implementations across Firefox.
**Improve browser reliability, performance, and resource efficiency:**Investigate and resolve issues impacting stability, correctness, and performance. Analyze and improve memory usage and efficiency within a complex, multi-threaded browser environment.
**Collaborate on security initiatives:**Partner with engineers across teams to identify, prioritize, and address security issues. Participate in debugging, root cause analysis, and implementation of effective long-term solutions.
**Contribute to technical design and planning:**Participate in technical discussions, design reviews, and project planning for security-related initiatives. Help evaluate tradeoffs and contribute to engineering decisions within your area of work.

What you’ll bring:

Strong software engineering and security fundamentals: Experience in software engineering, with proficiency in C/C++ and a solid understanding of security principles, including cryptographic protocols and implementations.
**Experience building and maintaining complex software systems:**Ability to contribute to the design, implementation, testing, and maintenance of software in large-scale or security-sensitive environments.
**Strong debugging and problem-solving skills:**Expertise in diagnosing and resolving issues in multi-threaded, cross-platform native applications, including performance and memory-related challenges.
**Collaborative and effective communicator:**Ability to work effectively with distributed teams, communicate technical concepts clearly, and collaborate constructively to solve problems.
Growth mindset and willingness to learn: Demonstrated curiosity and desire to deepen expertise in browser security, cryptography, and systems programming while continuously improving engineering skills.
**Web platform and modern systems experience:**Familiarity with web technologies and interest or experience in Rust. Comfortable working within large, complex, multi-language codebases.

What you’ll get:

Generous performance-based bonus plans to all eligible employees - we share in our success as one team
Rich medical, dental, and vision coverage
Generous retirement contributions with 100% immediate vesting (regardless of whether you contribute)
Quarterly all-company wellness days where everyone takes a pause together
Country specific holidays plus a day off for your birthday
One-time home office stipend
Annual professional development budget
Quarterly well-being stipend
Considerable paid parental leave
Employee referral bonus program
Other benefits (life/AD&D, disability, EAP, etc. - varies by country)

About Mozilla

Mozilla exists to build the Internet as a public resource accessible to all because we believe that open and free is better than closed and controlled. When you work at Mozilla, you give yourself a chance to make a difference in the lives of Web users everywhere. And you give us a chance to make a difference in your life every single day. Join us to work on the Web as the platform and help create more opportunity and innovation for everyone online.

Commitment to diversity, equity, inclusion, and belonging

Mozilla understands that valuing diverse creative practices and forms of knowledge are crucial to and enrich the company’s core mission. We encourage applications from everyone, including members of all equity-seeking communities, such as (but certainly not limited to) women, racialized and Indigenous persons, persons with disabilities, persons of all sexual orientation s, gender identities, and expressions.

We will ensure that qualified individuals with disabilities are provided reasonable accommodations to participate in the job application or interview process, to perform essential job functions, and to receive other benefits and privileges of employment, as appropriate. Please contact us at hiringaccommodation@mozilla.com to request accommodation.

We are an equal opportunity employer. We do not discriminate on the basis of race (including hairstyle and texture), religion (including religious grooming and dress practices), gender, gender identity, gender expression, color, national origin, pregnancy, ancestry, domestic partner status, disability, sexual orientation, age, genetic predisposition, medical condition, marital status, citizenship status, military or veteran status, or any other basis covered by applicable laws. Mozilla will not tolerate discrimination or harassment based on any of these characteristics or any other unlawful behavior, conduct, or purpose.

Group: D

#LI-REMOTE

Req ID: R3155

Hiring Ranges:

Remote Spain

€58.000—€77.000 EUR

Why Mozilla?

At Mozilla, we’re serving humanity—by maintaining a safe, open internet—while also helping the individual humans employed here to reach their personal and professional goals. With a relatively small team serving hundreds of millions of people, a culture of exploration, and a commitment to mentorship, opportunities abound to learn and grow at Mozilla.

Our values drive our actions

Purpose is built into our work, with our mission driving every decision
We challenge assumptions, the status quo, ourselves, and each other
We are transparent: in our code, our business partnerships, and our everyday interactions
We seek out people from diverse backgrounds and with perspectives different from our own
We pair purpose with performance and put people ahead of profit

Our impact is global

1000+ paid staff from over 30 countries
Thousands of volunteer contributors across six continents
2 global offices: Berlin and Toronto
9 coworking space locations: San Francisco, San Mateo, London, Paris, Portland, Tulsa, Vancouver, Chicago, and Bellevue
Hundreds of home offices globally

Our benefits are world-class

Flexible work environment (majority of Mozillians work remotely)
Industry-leading paid parental leave (up to 26 weeks of fully paid leave for childbearing parents and up to 12 weeks for non-childbearing parents)
Reimbursement for professional development (up to $3,000/year)
A work setup including the latest hardware and software of your choice

Senior Software Engineer, Firefox Security