Front‑End Engineer (Web Security) - Lisbon based/hybrid

We are looking for a curious, analytical, and detail‑oriented JavaScript/ Front End professional with a strong interest in understanding how malicious software operates within browser‑based applications, particularly web extensions. The ideal candidate has a solid background in code review and the ability to assess the true behavior of software beyond its declared functionality, and a strong motivation to identify security risks at scale.

This role requires a hands‑on technical profile with strong out‑of‑the‑box thinking, capable of auditing both submitted code and internal review tools to uncover potential security gaps. A proactive mindset, combined with strong analytical and investigative skills, is key to success in this position.

Key Responsibilities

· Analyze browser extension code using static and dynamic analysis techniques to identify security violations and malicious behavior.

· Perform code reverse engineering and debugging, primarily focused on JavaScript‑based front‑end technologies.

· Review extension source code to determine actual behavior versus declared functionality.

· Identify, document, and report security vulnerabilities, including impacted code areas and recommended remediation actions.

· Support the investigation and takedown of malicious browser extensions.

· Audit and assess internal review and detection tools to identify potential gaps or flaws.

· Identify emerging threat patterns and share insights with the team to improve detection capabilities.

· Define and implement rules and detection patterns to identify security violations at scale.

· Recommend and contribute to process improvements and automation to enhance efficiency and accuracy.

· Act as a technical consultant, providing guidance, clarification, and technical input to team members.

· Conduct code reviews and provide feedback aligned with secure coding best practices.

· Collaborate with cross‑functional teams and maintain clear, well‑structured technical documentation.

Required Skills

· Strong hands‑on experience with JavaScript, including advanced concepts such as closures, prototypes, variable scope, hoisting, callbacks, and object‑oriented principles.

· Proficiency in HTML and CSS.

· Solid experience in code review, with the ability to assess real behavior and intent.

· Experience working with database queries, such as SQL.

· Strong analytical mindset with curiosity and the ability to think creatively and critically.

Nice‑to‑Have Skills

· Knowledge of web application and cybersecurity fundamentals, including vulnerability assessment and remediation.

· Experience or familiarity with browser extensions and their lifecycle.

· Exposure to cybersecurity tools such as Burp Suite, Nmap, or similar open‑source tools.

· Understanding of malware categories and behaviors.

· Experience or familiarity with DAST and SAST methodologies.

· Understanding of obfuscation and de‑obfuscation techniques.

· Experience with Node.js, Webpack, and front‑end frameworks or libraries such as React, Angular, or jQuery.

· Strong experience in writing technical and security assessment reports.