Index: Firefox

A series documenting my patches to Mozilla Firefox as a Privacy Engineering intern.

This series covers my contributions to Firefox’s privacy and security features during my internship at Mozilla. Each post documents a specific patch: the problem it solved, the implementation, and what I learned shipping code to 200M+ users.

The Internship

Over the course of this internship I touched nearly every layer of the browser: JavaScript services in the parent process, Lit web components in content pages, C++ header files, Python build extensions, Kotlin GeckoView tests, Taskcluster CI pipelines, Fluent localization files, and JSON privacy lists. 40 commits across 23 bugs, spanning 9 distinct feature areas, plus an ML model for per-request tracker cost estimation.

The work started small (a one-line JSON change to strip a tracking parameter) and scaled up to cross-platform infrastructure (a pref extraction pipeline running daily against desktop and Android nightly builds), defensive hardening on a binary decoder consuming server-pushed data, and an XGBoost regression model packaged for in-browser ONNX inference. Along the way I passed a security review, coordinated multi-reviewer patches across 6 module ownership areas, and hosted an engineering event at the Mozilla Toronto office.

By the numbers:

  • 40 commits across 23 bugs
  • ~14,000 lines added, ~6,100 lines removed
  • Languages: JavaScript, Python, Kotlin, C++, HTML/CSS, YAML, Fluent, ONNX
  • Reviewers worked with: manuel, emz, timhuang, mconley, freddyb, and others

Projects

  1. Privacy Metrics Widget - Widget showing weekly tracker blocking stats on the protections dashboard
  2. Notifications Telemetry Pipeline - Glean telemetry for the full notification permission lifecycle
  3. Privacy Alignment - Auto-generated privacy capability docs from source code, desktop and Android
  4. Copy Clean Link - Stripping tracking parameters from copied URLs
  5. Clear Data Dialog - Modernizing the clear history dialog
  6. SmartBlock - Preserving useful content from blocked embeds, plus localization and probe maintenance
  7. Security - Topical explainers on defensive validation at browser trust boundaries
  8. Community Engagement - Events, talks, and networking at Mozilla
  9. Tracker Performance Cost Model - Multi-target XGBoost regression scoring tracker domains by performance cost