Security Engineer, Application Security

Writer

. Build security into the DNA of our AI platform by conducting threat modeling sessions with product teams, designing secure architectures for new features, and ensuring security considerations shape product decisions from day one—not after the fact .

Posted 5/12/2026full-timeLondon • 🇬🇧 United KingdomMid-LevelSeniorWebsite

Tech Stack

Tools & technologies

GoJavaJavaScriptPythonTypeScript

About the role

Key responsibilities & impact

Build security into the DNA of our AI platform by conducting threat modeling sessions with product teams, designing secure architectures for new features, and ensuring security considerations shape product decisions from day one—not after the fact
Own and evolve our application security program including establish and maintain SAST/DAST scanning in CI/CD pipelines, conducting security code reviews for critical changes, and building automation that catches vulnerabilities before they reach production
Partner with engineering teams to establish and champion secure coding standards, creating reusable security patterns and libraries that make it easier for developers to build securely by default
Design and recommend security features and products that help secure customer environments. You are the advocate and the vision for how we protect and secure customers.
Integrate and leverage AI agents to help increase velocity for the security team and the overarching engineering org to ensure that we are proactive in minimizing risk while we build products
Lead security assessments and penetration testing of WRITER's applications, AI services, and APIs, identifying vulnerabilities across our tech stack and working collaboratively with teams to remediate issues at scale
Design and implement security controls for protecting data pipelines, model training environments, and customer-facing AI agents
Stay ahead of emerging threats in the AI/ML security landscape, researching attack vectors specific to LLMs and generative AI, and proactively building defenses against novel risks

Requirements

What you’ll need

4+ years of hands-on experience in application security engineering, with a proven track record of securing large-scale production systems—bonus points if you've worked in fast-growing startups or high-growth environments
Understanding of developer experience and developer workflows for shipping features and products. You care deeply about reducing risk while considering velocity of engineers.
Technical expertise in at least two programming languages (Python, Java, Go, JavaScript/TypeScript) and the ability to read and review code across multiple languages, understanding both business logic and security implications
Knowledge of security tools and methodologies including SAST/DAST solutions, vulnerability management platforms, security testing frameworks, and DevSecOps practices—you know which tools to use and when automation beats manual review
Excellent communication skills that allow you to translate complex security concepts into clear recommendations for both technical and non-technical audiences—you can explain why something matters and motivate teams to action
A builder's mindset that looks for opportunities to automate, scale, and empower rather than create bottlenecks—you understand that security enables the business, not blocks it
Alignment with WRITER's values of Connect (building strong relationships across teams), Challenge (pushing the boundaries of what's possible in AI security), and Own (taking end-to-end responsibility for the security of our platform)

Benefits

Comp & perks

Generous PTO, plus company holidays
Comprehensive medical and dental insurance
Paid parental leave for all parents (16 weeks)
Fertility and family planning support
Early-detection cancer testing through Galleri
Competitive pension scheme and company contribution
Annual work-life stipends for:
Wellness stipend for gym, massage/chiropractor, personal training, etc.
Learning and development stipend
Company-wide off-sites and team off-sites
Competitive compensation and company stock options

ATS Keywords

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Applicant Tracking System Keywords

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Hard Skills & Tools

application security engineeringSASTDASTvulnerability managementsecurity testing frameworksDevSecOpsPythonJavaGoJavaScript

Soft Skills

communicationcollaborationproblem-solvingautomation mindsetrelationship buildingmotivationadaptabilityproactive risk managementclear recommendationsbuilder's mindset