Senior Application Security Engineer

Capital.com's Product Security team protects our web and mobile applications, infrastructure, and external perimeter in a highly regulated environment. As Senior/Staff Application Security Engineer, you will raise the bar for application security across the organisation. This role is measured by leverage: how well you design, automate, and scale security processes so that many engineering teams can build securely by default.

You will lead security architecture reviews and threat modelling, increasingly with the help of AI tooling, and turn one-off security work into repeatable, self-service capabilities. The role combines deep hands-on offensive and defensive security expertise with the engineering mindset needed to automate at scale. You will work closely with development, QA, DevOps, and platform teams.

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Responsibilities:

Security Architecture & Threat Modelling:

Lead security architecture reviews and threat modelling for new and existing systems, using AI tools to make reviews faster, more consistent, and scalable across teams

Act as a security force multiplier by influencing the standards, patterns, and guardrails that let teams move fast and stay secure

Security Automation & Tooling:

Design, build, and automate scalable security processes that engineering teams can self-serve, covering secure design review, threat modelling, testing, and remediation workflows

Integrate and automate security checks across the SDLC and CI/CD pipelines (SAST, DAST, SCA, secrets, and IaC scanning), tuned for strong signal and low friction

Own and evolve security tooling such as DefectDojo and SAST, DAST, and SCA platforms, maximising automation, coverage, and integration

Apply AI and LLM-based tooling to architecture review, threat modelling, code review, and vulnerability triage, and help define how the team adopts these tools safely

Security Testing & Vulnerability Management:

Conduct and oversee security assessments of web and mobile applications, APIs, and cloud infrastructure, including manual testing and PoC development

Run vulnerability scans across internal infrastructure and the external perimeter, then analyse findings, define remediation, and track issues to closure

Support and triage the Bug Bounty Program and external vulnerability reports, automating triage where possible

Participate in and help lead red teaming and offensive security exercises

Enablement:

Drive knowledge sharing on secure development, mentor engineers, and deliver training for development and QA teams

Requirements:

Experience:

5+ years in application or product security, or equivalent depth, with a track record of senior or staff-level impact

Demonstrable experience leading security architecture reviews and threat modelling (e.g. STRIDE, attack trees, data-flow analysis) across multiple teams or products

Proven ability to automate and scale security processes by building tooling, integrations, and self-service workflows that reduce manual effort

Technical:

Strong hands-on security testing skills, including code review and web, mobile, and API application security assessments, as well as the ability to triage and validate external vulnerability reports and bug bounty submissions

Strong software engineering ability in at least one language (e.g. Python, Go, JavaScript), with the ability to build automation, not just scripts

Deep understanding of the OWASP Top Ten, secure design, and secure coding best practices

Experience with SAST, DAST, SCA, and vulnerability management platforms, and integrating them into CI/CD

Strong understanding of modern application architectures: REST APIs, microservices, cloud-based systems, and containers

Practical experience applying AI and LLM tooling to security work, or clear enthusiasm and aptitude to do so

Collaboration:

Excellent communication and influencing skills: you can explain security concepts to technical and non-technical stakeholders and drive change without direct authority

A self-starter who enjoys solving complex problems, building leverage through automation, mentoring others, and strengthening security culture

Nice to have:

Experience securing the AI harness: hardening LLM and agent pipelines, prompts, tool and MCP integrations, and model endpoints against prompt injection, data leakage, and insecure agent actions

Experience securing Kubernetes, including cluster hardening, RBAC, network policies, admission control, workload isolation, and image and supply-chain security

Experience securing AWS infrastructure, including IAM, network and account architecture, key and secret management, and CSPM

Experience building AI-assisted security tooling or internal self-service security platforms

Experience mentoring or technically leading a security team

Offensive or advanced security certifications such as OSAI, OSEP, OSCP, or OSWE

What you'll get in return:

You will join the company, that cares about work and life balance

Annual Bonus based on the performance review cycle

Generous Annual Leave Policy

Medical Insurance and Pension fund, with additional benefit packages based on the location

Hybrid working model (3 days from our modern office and 2 days fully remotely)

Comprehensive Workation Policy with 30 more remote days available.

Possibility of taking two additional days of paid leave per year to dedicate to volunteering efforts.

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