Senior Firefox Security Engineer

Website mozilla Mozilla

Mozilla is looking for a Security Hardening Engineer to help improve the security of Mozilla desktop and mobile browsers. As part of the Platform Security Team, you will develop new hardening features that help protect users from malware threats and code injection and develop tools and instrumentation to better understand these threats. If you’re passionate about stopping the bad guys from ruining user experience, data safety, and privacy, and you want to be part of an elite team fighting to protect our users, we want to hear from you!

As a Security Hardening Engineer at Mozilla, you will…

  • Develop tools and instrumentation for analyzing code injection and its side effects on application stability and performance.
  • Develop application features which prevent or control code injection
  • Work on general hardening development features (memory allocation, JS engine, static analysis, sandboxing, WebAssembly)
  • Assist in security response to application exploits
  • Research new and existing hardening methods and features


  • Experience in security auditing, code review and security testing.
  • Proficient in finding and analysing security flaws in native code – i.e. through code auditing, debugging, code instrumentation etc.
  • Programming experience in C++, JavaScript, Python and/or Rust
  • Sufficient C++ and x86-64 assembly language experience to reverse engineer, debug, and prevent malware and code injection techniques.
  • Strong grasp of multithreaded programming
  • A general understanding of web technologies (HTML, CSS and JavaScript).

Areas of Interest

  • Desktop development expertise on Windows.
  • Experience or interest in desktop operating system software development – user input and interface, events, component interfacing, Win32, COM.
  • Experience or interest in system level hacking: multi-threading, inter-process communication (IPC), memory allocation, synchronization, security sandboxing, Windows internals.
  • Code injection methods and prevention.
  • Experience with parsing executable file formats.


  • Comfortable working within an open source community, good natured and patient.
  • Interest in debugging large, complex client side applications using currently available tools based on user bug reports and feedback.
  • Written and verbal communication skills in English.

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.

We are an equal opportunity employer and value diversity. We do not discriminate on the basis of race, religion, color, national origin, gender, sexual orientation, age, marital status, veteran status, or disability status.

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