Security Engineer (Application Security, United Kingdom)

Join WRITER, a leading AI platform, as a Security Engineer. In this role, you'll build the security foundations that protect our AI systems, working at the intersection of application security, AI infrastructure, and developer enablement. You'll conduct threat modeling sessions, own and evolve our application security program, and design security features and products. This hybrid position is based in our London office and offers a range of benefits, including health insurance, stock options, and a learning and development stipend.

About Writer

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

Responsibilities

• Construire les fondations de la sécurité qui protègent les systèmes d'IA, en intégrant la sécurité dans chaque ligne de code.
• Posséder et faire évoluer le programme de sécurité des applications, y compris l'établissement et le maintien de l'analyse SAST/DAST dans les pipelines CI/CD.
• Diriger les évaluations de sécurité et les tests de pénétration des applications, des services d'IA et des API de WRITER, en identifiant les vulnérabilités.
• 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)

Requirements

• 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
• 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
• 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
• Understanding of developer experience and developer workflows for shipping features and products. You care deeply about reducing risk while considering velocity of engineers
• 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