MozillaHiring

Senior Software Engineer, Firefox Security

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

Security engineering role on a web browser, writing low-level code in C or C++ to harden the product; remote-friendly with distributed teams.

About the role

The work centers on browser security: isolation of privileges, trust boundaries, cryptography and web APIs, plus diagnosing crashes and memory problems in a large multithreaded codebase.

At a glance

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

What you will do

  • Build, test and ship security and hardening features for enterprise users
  • Improve core security mechanisms such as cryptographic protocols, WebPKI and sensitive web APIs
  • Investigate security issues across teams, find root causes and land maintainable fixes
  • Diagnose stability, correctness, performance and memory problems in multithreaded code

What they look for

  • Three or more years in low-level engineering, strong in C and/or C++
  • Grasp of security fundamentals
  • Experience debugging cross-platform native apps with memory and performance issues
  • Familiarity with HTML, CSS and JavaScript, plus interest in Rust
  • Clear technical writing and comfort working with distributed teams

Nice to have

  • Experience with Rust

Benefits

  • Performance-based bonus plans for eligible staff
  • Retirement contributions vested immediately
  • Quarterly company-wide wellness days
  • One-time home office stipend and yearly learning budget
  • Paid parental leave and referral bonuses

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Claude

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Muse

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Message for Muse
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Muse is available in the US only for now.

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Questions about this job

Can I do this job remotely, and from which countries?

The posting lists it as remote for people in Spain.

What does this job pay?

The posting does not state a salary, so there is no figure to quote.

What experience is needed?

It is a senior role. The posting asks for: three or more years in low-level engineering, strong in C and/or C++; grasp of security fundamentals; experience debugging cross-platform native apps with memory and performance issues. Skills it names include Rust, HTML, CSS, JavaScript.

How do I apply with Keywordise AI?

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