Work on Firefox Security to design, implement, test, and ship security features (including privilege isolation, cryptographic protocols, and WebPKI), diagnose multithreaded stability/performance issues, and collaborate across teams. Requires 3+ years in low-level systems programming with strong C/C++ proficiency and familiarity with web technologies and Rust. Role listed as Remote Sweden.

Work on designing, implementing, testing, and shipping security and hardening features for Firefox across multiple operating systems. Improve core security mechanisms (cryptographic protocols, WebPKI, security-sensitive web APIs), investigate and fix security issues, and diagnose stability, performance, and memory problems in a large multi-language codebase. Requires 3+ years in low-level systems programming with strong C/C++ skills and familiarity or interest in Rust.

Design, implement, test, and ship security and hardening features for enterprise Firefox users; improve core security architecture (cryptographic protocols, WebPKI, security-sensitive web APIs) and build privilege isolation. Diagnose and resolve stability, correctness, performance, and memory issues in a complex, multithreaded, cross-platform native codebase. Requires 3+ years of low-level systems programming experience with strong proficiency in C and/or C++ and familiarity with Rust and web technologies.

Work on designing, implementing, testing, and shipping security and hardening features for Firefox across multiple operating systems. Improve core security mechanisms (cryptographic protocols, WebPKI, security-sensitive web APIs), investigate and fix security issues, and diagnose stability, performance, and memory problems in a large, multithreaded codebase. Requires 3+ years in low-level systems programming with strong C/C++ proficiency and security fundamentals; familiarity with web technologies and Rust is desirable.

Join Firefox Security to build and improve security architecture across platforms (privilege isolation, cryptographic protocols, WebPKI, security-sensitive APIs). Responsibilities include designing, implementing, testing, and shipping security features; investigating security issues and fixing stability, performance, and memory problems in a multithreaded, cross-platform codebase. Requires 3+ years low-level/software systems experience, strong C/C++ proficiency, familiarity or interest in Rust and web technologies, and experience working with distributed teams. Salary range listed for Remote UK: £66,000–£87,000.

Work on designing, implementing, testing, and shipping security and hardening features for Firefox, improving security architecture (including cryptographic protocols and WebPKI), investigating and fixing security issues, and diagnosing stability, correctness, performance, and memory problems in a large, multithreaded, cross-platform codebase. Requires 3+ years of low-level systems programming experience, strong C/C++ proficiency, security knowledge, and familiarity with web technologies and Rust.

Work on Firefox Security to design, implement, test, and ship security features (privilege isolation, cryptography, WebPKI, security-sensitive web APIs), investigate and fix security issues, and improve reliability and performance in a complex, multithreaded, cross-platform codebase. Requires 3+ years in low-level systems programming with proficiency in C and/or C++ and familiarity or interest in Rust.

Join the geographically distributed Firefox Performance team to identify and fix browser performance bottlenecks, write code and tests, build prototypes, drive cross-team performance work, contribute to benchmarks and tooling, and own performance for significant areas of the browser. Requires 5+ years relevant experience, deep C++ proficiency, working JavaScript skills, and experience with profiling tools (e.g., VTune, Xperf).

Mozilla seeks an experienced browser engine engineer to investigate browser behavior, prototype engine-level changes, instrument and measure performance and correctness, and work closely with a small cross-disciplinary team. Requires substantial experience with browser internals (e.g., DOM, layout, rendering, JS runtimes), strong C++ or Rust skills, profiling and testing practices, and the ability to build scripting/tools and prototypes. Hiring ranges for Canada are provided in the posting.

Mozilla seeks a senior staff-level browser engineer to design and implement experiments in browser engine subsystems (DOM, layout, rendering, JS runtimes, accessibility, etc.), prototype engine capabilities, instrument and measure performance and correctness, and work closely with a small technical team. Strong systems expertise in C++ or Rust, profiling, concurrency, and working in large codebases is required; experience with AI tools and open-source browser projects is a plus.

Work to finish or verify diagnoses of long-tail WebCompat/site-breakage bugs, reproduce and triage incoming reports, write WebCompat interventions and simple (often AI-assisted) fixes and land them. Requires solid web development (HTML, CSS, JavaScript), strong browser devtools and cross-browser debugging skills; Gecko and prior WebCompat/web-standards experience are preferred.

Thunderbird seeks a Staff Product Engineer for Thunderbolt (enterprise AI). The role focuses on full-stack development (TypeScript/JavaScript, component-based front ends, APIs, backend services), diagnosing and fixing issues across application and infrastructure layers, supporting partner-hosted and customer-controlled deployments, and producing documentation and runbooks. Experience with LLM/RAG/agents, enterprise deployment concerns (authentication, identity, observability, reliability), and customer-facing implementation work is required. This is a remote, full-time position for candidates residing and authorized to work in Canada.

Join Thunderbird’s Thunderbolt team as a Staff Full‑Stack Product Engineer to build and ship front-end and back-end features, integrations, and customer-specific customizations for enterprise AI deployments. The role works directly with technical partners and enterprise customers to deploy, stabilize, and maintain pilot and production environments, diagnose complex cross-stack issues, and convert recurring needs into product capabilities. Requires 10+ years of professional software engineering experience and strong full‑stack skills (TypeScript/JavaScript, component front ends, APIs), plus experience with AI-enabled applications and enterprise deployment concerns.

Responsible for end-to-end payroll processing for approximately 800 U.S. and Canadian employees on a semi-monthly basis, ensuring compliance with federal, state/provincial, and local payroll tax regulations. Own payroll issue resolution, partner with People Operations, Benefits and external vendors, assist with year-end activities (W-2s, T4s, tax filings, audits), and drive process improvements while mentoring a Payroll Administrator.

Lead North America payroll operations, processing semi-monthly payroll for approximately 800 U.S. and Canadian employees; ensure compliance with federal, state/provincial, and local payroll tax regulations; manage payroll issue resolution, benefits coordination, year-end activities (W-2s, T4s), and drive process improvements while mentoring a Payroll Administrator. Requires 7+ years payroll experience; ADP Workforce Now experience preferred.

The Senior Financial Analyst (Core Services) prepares recurring forecasts and monthly budget updates, reconciles actuals through close, maintains headcount and vendor/cloud spend tracking, and produces variance and driver analyses for budget owners and the COO. The role emphasizes financial modeling, automation/AI to improve recurring processes, partnership with Accounting and People, and working across functions to communicate results to non-finance audiences.

Responsible for preparing recurring forecasts and monthly budget updates (using Pigment), reconciling actuals through close, maintaining position-level headcount tracking, monitoring vendor and cloud spend, and applying AI/automation to recurring finance processes. Requires 5+ years in FP&A or similar, advanced financial modeling and spreadsheet skills, experience with enterprise planning tools and NetSuite, and familiarity with cloud cost/FinOps concepts.

Partner with Sales to lead technical discovery, design, pilots and rollouts of Firefox Enterprise across DACH (Germany/Austria/Switzerland). Run workshops, validate integrations (SSO/MFA, SIEM, proxies, PKI), create reference architectures and enable partners. Remote Germany; hiring range €81,000–€108,000 EUR per year.

Mozilla seeks a Senior Security Engineer (Incident Responder) to monitor and mitigate attacks across products and services. Responsibilities include incident command, designing alerts/playbooks/automation, threat hunting, and managing SIEM/EDR/SOAR tooling. Requires 5+ years of incident response or SOC/PSIRT/CSIRT experience and hands-on experience with SIEM (Splunk/ELK/BigQuery), EDR, SOAR (Tines/Splunk SOAR), and cloud platforms. Hiring range for Remote Spain: €58,000–€77,000 per year.

Mozilla is hiring a Senior Security Engineer (Incident Responder) to monitor and mitigate attacks across products and services. Responsibilities include leading incident response lifecycle as incident commander, designing alerts/playbooks/automation for 24/7 response, threat hunting, triage, and post-mortem activities. Requires 5+ years in security incident management or SOC/PSIRT/CSIRT experience and practical expertise with SIEM (e.g., Splunk, ELK, BigQuery), EDR tools, SOAR platforms (e.g., Tines, Splunk SOAR), and cloud environments (GCP, AWS, Azure, Heroku).