OverviewAs a Security Engineer, you design and implement security features that strengthen Firefox, across multiple operating systems.
You collaborate to improve Firefox's core security posture, including cryptographic protocols and WebPKI, while addressing issues and ensuring reliability in a complex, multithreaded browser environment.
You will work with cross-functional teams to ship robust fixes and drive security initiatives.
This role offers meaningful impact in advancing a privacy-minded, open-source web platform.
Compensaciones / Beneficiosgenerous performance-based bonus
retirement contributions with immediate vesting
quarterly wellness days
holiday policies plus birthday off
home office stipend
annual professional development budget
ResponsabilidadesDesign, implement, test, and ship security features for enterprise users to strengthen Firefox security
Advance Firefox security architecture across operating systems with privilege isolation and trust boundary improvements




Strengthen core security mechanisms including cryptographic protocols, WebPKI, and sensitive web APIs
Collaborate across teams to investigate security issues, identify root causes, and deliver robust fixes
Diagnose and improve browser reliability, performance, and memory usage in a multithreaded environment
Requisitos principales3+ years of low-level software engineering
Proficiency in C and/or C++
Solid understanding of security fundamentals
Experience debugging multithreaded, cross-platform native applications
Familiarity with web technologies (HTML, CSS, JavaScript) and interest/experience in Rust
Ability to work effectively within large, multi-language codebases
Strong communication and collaboration in distributed teams
effective collaboration
clear written and verbal communication
problem-solving
C/C++
security fundamentals
multithreading

📌 Senior Software Engineer, Firefox Security (España)
🏢 Mozilla
📍 España