MozillaHiring

Senior Software Engineer, Firefox Security

  • Remote, France
  • Senior
  • Posted 2 weeks ago
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In one line

Senior security engineering job on a browser team, building hardening features and improving security architecture across operating systems.

About the role

This suits an engineer who likes low-level systems work and security problems in equal measure, and who can reason about trust boundaries in a large codebase. The work spans enterprise hardening and core browser security mechanisms.

At a glance

Pay
Not stated in the posting
Remote scope
Remote, France
Seniority
Senior
Skills
Rust, HTML, CSS, JavaScript, WebPKI
Posted
14 Oct 2026
Last checked
28 Oct 2026

What you will do

  • Design and ship security and hardening features for enterprise users
  • Advance security architecture across operating systems through privilege isolation and trust boundary changes
  • Improve cryptographic protocols, WebPKI and security-sensitive web APIs
  • Investigate security issues across teams, find root causes and deliver maintainable fixes
  • Resolve stability, correctness, performance and memory problems in a multithreaded environment

What they look for

  • 3+ years in low-level software engineering
  • Strong proficiency in C and/or C++
  • Solid understanding of security fundamentals
  • Experience with multithreaded, cross-platform native applications and their memory and performance issues
  • Familiarity with HTML, CSS and JavaScript, plus interest or experience in Rust
  • Ability to work in large, complex, multi-language codebases

Benefits

  • Performance-based bonus, retirement contributions with immediate vesting, wellness days, home office stipend, professional development budge

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How to connect

Questions about this job

Is this job fully remote, and from where?

Yes. The posting lists Senior Software Engineer, Firefox Security as a remote role for candidates in France.

What does this job pay?

No pay range is stated in the posting.

What experience is needed?

It is a senior role. The posting asks for: 3+ years in low-level software engineering; strong proficiency in C and/or C++; solid understanding of security fundamentals. Skills it names include Rust, HTML, CSS, JavaScript.

How do I apply with Keywordise AI?

Click Apply with Keywordise AI, create an account and upload your CV. Your CV and cover letter are written for this job from what you have really done, then Keywordise applies for you. Trial: 7 days, no card.

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