Senior Software Engineer, Browser Automation
Horizon3 AI3 months ago
Remote, United StatesSenior
Base Salary
$169k - $208k/yr
Responsibilities
- Grow and harden the browser automation and crawling engine that discovers, navigates, and interacts with target applications during autonomous penetration tests.
- Advance browser-driven crawling with Playwright and Stagehand.
- Handle SPA routing and hydration timing, authenticated sessions, multi-step flows, file uploads, WebSocket and Socket.IO traffic, infinite scroll, and crawler traps.
- Extend agentic login and authentication capabilities, including complex authentication flows, MFA/TOTP, and reliable unattended credentialed access.
- Improve crawl coverage, determinism, throughput, endpoint and parameter discovery, deduplication, queueing, and state management while maintaining production safety.
- Apply deterministic automation and LLM-driven navigation appropriately to keep the system fast, debuggable, and cost-effective.
- Collaborate with attack-team engineers consuming crawl output and help shape the graph-backed application map used by the broader pipeline.
Requirements
- Production software development experience with deep hands-on browser automation experience using Playwright, Puppeteer, or Selenium against complex web applications.
- Strong TypeScript and Node.js skills, with familiarity with Chromium internals, the Chrome DevTools Protocol, network interception, the DOM, and JavaScript execution contexts.
- Experience handling flaky, stateful, JavaScript-heavy applications, including SPA timing, authentication, and anti-automation defenses.
- Understanding of distributed and concurrent systems, including queues, backpressure, retries, idempotency, and reliable execution of many browser sessions.
- Ability to prioritize deterministic, debuggable automation and use LLMs selectively when appropriate.
- Experience owning critical production subsystems through reliable unattended operation at scale.
- Preferred experience with Stagehand, Browser Use, or similar agentic browser frameworks and LLM-in-the-loop automation.
- Preferred background in web application security or offensive tooling, including familiarity with broken access control, IDOR/BOLA, SQL injection, XSS, SSRF, or SSTI.
- Preferred familiarity with graph data models such as Neo4j, large-scale crawling, client-side JavaScript analysis, endpoint discovery, or automated session and credential management.
- Experience hacking on browser automation tool internals, operating automation at extreme scale, bypassing sophisticated WAF and anti-bot defenses, or deploying LLMs in production is a differentiator.
Benefits
- Remote and hybrid work models are available depending on role and location, including a Chicago office with regular in-office presence for some roles.
- Health, vision, and dental insurance are provided for employees and their families.
- Flexible vacation policy.
- Generous parental leave.
- Full-time roles are eligible for equity in the form of stock options.
- Inclusive, collaborative culture with career development opportunities.
Tech Stack
About Horizon3 AI
Horizon3 AI builds NodeZero, a proactive security platform that autonomously performs penetration testing and validates attack paths across on‑prem, cloud, and hybrid environments. The company sells its software by subscription to security and IT teams at enterprises and government agencies, helping prioritize and verify fixes. Founded in 2019 and headquartered in San Francisco, it is privately held and serves customers across regulated industries and the public sector.