About this Senior Application Security Engineer role at Capital
Capital · Hybrid · Warsaw, Mazowieckie, Poland
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.
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
- 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
- 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
- Drive knowledge sharing on secure development, mentor engineers, and deliver training for development and QA teams
Security Automation & Tooling:
Security Testing & Vulnerability Management:
Enablement:
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
- 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
- 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
Technical:
Collaboration:
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:
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