MozillaHiring

Senior Software Engineer, Firefox Security

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

Senior engineering role focused on browser security features and architecture, working in a large native codebase with distributed colleagues.

About the role

Security feature work and architecture changes for a widely used browser are what this person will own, from design through testing and release. The role sits with a distributed team that investigates issues across the codebase.

At a glance

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

What you will do

  • Design, implement, test and release security features that make the browser harder to attack
  • Push improvements to core security posture, such as privilege isolation and shifted trust boundaries
  • Strengthen cryptographic protocols, WebPKI and security-sensitive web APIs
  • Investigate security problems with other teams and deliver fixes that are easy to maintain
  • Tackle stability, correctness, performance and memory issues in a multithreaded environment

What they look for

  • 3 or more years of low-level software engineering experience
  • Strong C and/or C++ skills and a solid understanding of security fundamentals
  • Debugging experience with multithreaded, cross-platform native apps
  • Knowledge of HTML, CSS and JavaScript, and interest or experience in Rust
  • Clear written and spoken communication with distributed teams

How Keywordise applies for you

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Claude

  1. In Claude, open Settings, then Connectors, and choose Add custom connector.
  2. Name it Keywordise and paste the connector URL.
  3. Click Connect, log in to Keywordise and approve. Then send the prompt in a new chat.
Connector URL
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ChatGPT

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  2. Add a new connector with the connector URL and choose OAuth. Leave the client ID and secret empty.
  3. Log in to Keywordise and approve. Then send the prompt in a new chat.
Connector URL
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Muse

  1. Open Muse (muse.ai or the app) and send it the message below.
  2. If Muse asks how to sign in, answer OAuth. Open the sign-in link it sends, log in to Keywordise and approve.
  3. Send the prompt. Muse asks before it sends anything.
Message for Muse
Add a custom connector called Keywordise. It is a remote MCP server at https://keywordise.com/mcp and uses OAuth. Give me the sign-in link.

Muse is available in the US only for now.

Prompt
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How to connect

Questions about this job

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

Yes, it is listed as remote, aimed at candidates in Finland.

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: 3 or more years of low-level software engineering experience; strong C and/or C++ skills and a solid understanding of security fundamentals; debugging experience with multithreaded, cross-platform native apps. Skills it names include Rust, HTML, CSS, JavaScript.

How do I apply with Keywordise AI?

Select Apply with Keywordise AI, sign up and upload your CV. Keywordise writes a CV and a cover letter for this job from your real experience and applies for you. The 7-day free trial needs no card.

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