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Writer is an enterprise generative AI platform that enables leading companies like Mars, Marriott, Uber, and Vanguard to build and deploy AI agents grounded in their data. The company is valued at $1.9B and backed by top-tier investors including Premji Invest, Radical Ventures, and ICONIQ Growth.
As a Security Engineer in Application Security, you will build security foundations that protect the AI systems powering enterprise customers. This role sits at the intersection of application security, AI infrastructure, and developer enablement, partnering with engineering teams to embed security into every line of code while maintaining platform trustworthiness.
Key responsibilities include:
- Conduct threat modeling sessions with product teams and design secure architectures for new AI features, ensuring security shapes product decisions from inception
- Own and evolve the application security program: establish and maintain SAST/DAST scanning in CI/CD pipelines, conduct security code reviews for critical changes, and build automation to catch vulnerabilities before production
- Partner with engineering teams to establish secure coding standards, creating reusable security patterns and libraries that enable developers to build securely by default
- Design and recommend security features and products that help secure customer environments, serving as the advocate and vision for customer protection
- Integrate and leverage AI agents to increase velocity for the security and engineering teams while proactively minimizing risk
- Lead security assessments and penetration testing of Writer's applications, AI services, and APIs, identifying vulnerabilities across the tech stack and collaborating on remediation 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 AI/ML security, researching attack vectors specific to LLMs and generative AI, and proactively building defenses against novel risks
This is a hybrid role based in the London office, reporting to the head of security engineering.
REQUIREMENTS:
- 4+ years of hands-on experience in application security engineering with a proven track record of securing large-scale production systems (bonus: experience in fast-growing startups or high-growth environments)
- Understanding of developer experience and workflows; ability to reduce risk while considering engineering velocity
- Technical expertise in at least two programming languages (Python, Java, Go, JavaScript/TypeScript) with 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
- Excellent communication skills to translate complex security concepts into clear recommendations for technical and non-technical audiences
- Builder's mindset focused on automation, scaling, and empowerment rather than creating bottlenecks; understanding that security enables the business
- Alignment with Writer's values: Connect (building strong relationships across teams), Challenge (pushing boundaries in AI security), and Own (taking end-to-end responsibility for platform security)
About Writer
AI / Data / Infrastructure; SaaS / Enterprise Software — enterprise generative AI platform for business teams.
