JavaScript Frontend Engineer (Web Security) - Lisbon based/hybrid
Cognizant · Lisboa, Lisbon, Portugal
About this role
The candidate will be responsible for analyzing, reverse engineering, and securing browser-based applications, specifically focusing on web extensions. Key tasks include performing static and dynamic analysis to detect security violations and malicious behavior in extension code. The role involves identifying and documenting vulnerabilities, supporting the investigation and takedown of malicious extensions, and defining detection rules at scale. The engineer will work with a JavaScript-heavy environment, utilizing tools like Node.js and Webpack, and will collaborate with cross-functional teams to improve security workflows and automation. The position requires deep knowledge of JavaScript internals and front-end technologies to effectively conduct code reviews and root cause analysis.
Skills & technologies
Must have
Nice to have
- Cybersecurity
- DAST
- SAST
- Burp Suite
- Nmap
- Obfuscation
- De-obfuscation
Read full description
English Required / Based in Lisbon, Portugal / Hybrid
We are seeking a skilled JavaScript Engineer with a strong background in web technologies and cybersecurity to analyze, reverse engineer, and secure browser‑based applications, with a particular focus on web extensions. This role involves identifying malicious behaviors, conducting security assessments, and driving automation and process improvements within the security analysis lifecycle.
Key Responsibilities
Analyze web extension code using static and dynamic analysis techniques to detect security violations and malicious behavior.
Perform JavaScript reverse engineering and debugging to understand complex or obfuscated codebases.
Identify, document, and report security vulnerabilities, including root cause analysis and recommended remediation steps.
Support the takedown and investigation of malicious browser extensions.
Conduct regular code reviews and provide constructive feedback aligned with secure coding best practices.
Analyze JavaScript code to identify malicious activities and, when necessary, reverse engineer the code.
Define and implement detection rules and security patterns to identify violations at scale.
Identify emerging threat patterns and share insights to enhance team detection capabilities.
Drive innovative ideas, recommend improvements, and help design and implement automation for existing processes.
Act as a technical consultant, providing guidance, clarification, and technical grooming to team members.
Collaborate effectively with cross‑functional teams and maintain clear technical documentation.
Contribute to continuous improvement of security workflows and tooling.
You Are Someone Who Brings
Strong hands‑on experience with JavaScript, including advanced concepts such as closures, prototypes, variable scope, hoisting, callbacks, and OOP principles.
Required Hands‑on Experience With HTML And CSS.
Required knowledge of JSON, AJAX, and ES6/ES7 standards.
Good understanding of Node.js and Webpack.
Experience working with front‑end frameworks or libraries such as React, Angular, or jQuery.
Strong code analysis, debugging, and reverse engineering skills, particularly in JavaScript applications.
Ability to analyze JavaScript code and identify malicious activities effectively.
Good communication skills and the ability to work as a collaborative team player.
Added Advantages (Nice To Have)
Cybersecurity experience or strong security knowledge.
Familiarity with DAST and SAST methodologies.
Knowledge of cybersecurity open‑source tools such as Burp Suite, Nmap, or similar tools.
Understanding of obfuscation and de‑obfuscation techniques.
Experience writing technical and security assessment reports.
