Senior Security Specialist – Penetration Testing

London Stock Exchange Group; Greater London; Remote; GBP 80,000 - 120,000; Full time

Benefits offered by this job

Healthcare

Retirement planning

Paid volunteering days

Wellbeing initiatives

Job summary

London Stock Exchange Group (LSEG) seeks a Senior Penetration Tester to join our internal offensive security team. This hands-on, highly technical role plans and executes penetration tests across systems and applications, uncovering vulnerabilities and raising security standards.

You will own engagements end-to-end, write technical reports, and collaborate with engineering teams to remediate findings. Experience with cloud, containers, and enterprise environments is essential; strong English

Qualifications

• Hands-on pentesting of web apps, APIs, thick clients, and infra.

Responsibilities

• Conduct in-depth penetration tests on applications, infrastructure, and cloud environments.
• Own assigned pentesting engagements end-to-end with limited oversight.
• Document findings clearly and provide actionable remediation guidance.
• Collaborate with application teams to scope, execute, and report security assessments.

Skills

Penetration testing

Burp Suite

Scripting

Automation

Cloud platforms

Docker

Kubernetes

Technical reporting

English communication

Tools

Burp Suite

Job description

LSEG is seeking aSenior 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. Engagement details (who, what, when, where). Testing team members and roles. Tools and methodologies used. Schedule and timelines. Target systems and environments. ConstraintSenior Security Specialist – Penetration Testing s, exclusions, and limitations. 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.

Career Stage: Senior Associate

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. Working with us means that you will be part of a dynamic organisation of 25,000 people across 65 countries. However, we will value your individuality and enable you to bring your true self to work so you can help enrich our diverse workforce. We are proud to be an equal opportunities employer. This means that we do not discriminate on the basis of anyone’s race, religion, colour, national origin, gender, sexual orientation, gender identity, gender expression, age, marital status, veteran status, pregnancy or disability, or any other basis protected under applicable law. Conforming with applicable law, we can reasonably accommodate applicants' and employees' religious practices and beliefs, as well as mental health or physical disability needs. You will be part of a collaborative and creative culture where we encourage new ideas. We are committed to sustainability across our global business and we are proud to partner with our customers to help them meet their sustainability objectives. Our charity, the LSEG Foundation provides charitable grants to community groups that help people access economic opportunities and build a secure future with financial independence. Colleagues can get involved through fundraising and volunteering. LSEG offers a range of tailored benefits and support, including healthcare, retirement planning, paid volunteering days and wellbeing initiatives.

Explore our divisions. LSEG is headquartered in the United Kingdom, with significant operations in 70 countries across Europe, the Middle East, Africa, North America, Latin America and Asia Pacific.

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