Senior Security Specialist – Penetration Testing

LSEG is seeking a Senior Penetration Tester to join our internal offensive security team. This role is hands-on and deeply technical, responsible for planning and executing penetration tests across a wide range of systems and applications. The successful candidate will be a skilled offensive security professional with a passion for uncovering vulnerabilities and improving security posture through rigorous testing and collaboration.

Key Responsibilities

Conduct in-depth penetration tests on applications, infrastructure, and cloud environments.

Take full ownership of assigned pentesting engagements end-to-end and deliver with limited oversight.

Compile technical scoping documents, track and document assessment metadata

Testing activities and event logs

Document findings clearly and concisely, providing actionable remediation guidance.

Collaborate with application teams to scope, execute, and report on security assessments.

Contribute to team improvement efforts and ensure all initiatives and feedback are well documented for future references.

Contribute to the continuous improvement of testing methodologies, tooling, automation.

Stay current with emerging threats, vulnerabilities, and offensive security techniques.

Participate in R&D initiatives as guided from leadership.

Support knowledge sharing and mentoring within the team.

Develop and maintain custom tools, scripts, and exploits to support testing activities.

Required Skills & Experience

Proven hands-on experience in penetration testing of Web Applications, APIs, Thick Client and Common Infrastructures (Active Directory, Cloud and Cloud-native based environments).

Proficiency with tools such as Burp Suite, common command-line tools, and ability to write custom scripts when needed.

Experience in automating pentesting tasks.

Strong understanding of application security, network protocols, and operating systems.

Experience with cloud platforms (AWS, Azure, GCP) and containerized environments (Docker, Kubernetes).

Ability to write clear, technical reports and communicate findings to both technical and non-technical stakeholders.

Experience working in large, complex enterprise environments.

Fluent communication skills in English, both written and verbal.

Relevant certifications and engagement with the security community is a plus

Threat Modelling experience is a plus.

Experience working in large, complex enterprise environments.

Proven track record of successfully managing and executing security engagements for various organizations with differing operational and technical profiles.

Ability to identify, assess, and communicate technical and project risks to stakeholders.

Understanding project requirements and aligning deliverables with agreed upon objectives and timelines.

London Stock Exchange Group (LSEG) Information

Join us and be part of a team that values innovation, quality, and continuous improvement. If you're ready to take your career to the next level and make a significant impact, we'd love to hear from you.

LSEG is a leading global financial markets infrastructure and data provider. Our purpose is driving financial stability, empowering economies and enabling customers to create sustainable growth.

Our purpose is the foundation on which our culture is built. Our values of Integrity, Partnership, Excellence and Change underpin our purpose and set the standard for everything we do, every day. They go to the heart of who we are and guide our decision making and everyday actions.