Senior Security Engineer - Mobile & Application Security

Arcus Search; Greater London; Remote; GBP 90,000 - 120,000; Full time

Job summary

Arcus Search is assisting a leading financial technology company in the UK to hire two Senior Security Engineers focused on mobile and application security. You will work hands-on with mobile and backend teams to design and implement security controls across the development lifecycle.

The role emphasizes secure mobile app development, API security, and collaboration with product managers to embed security throughout projects. Hybrid/remote options are available in the UK.

Qualifications

• Proven experience in application security roles (App Sec / Product Sec / Mobile).
• Strong knowledge of mobile-to-API interaction patterns and attack vectors.
• Hands-on security work with engineering teams across mobile and backend systems.

Responsibilities

• Secure mobile applications (iOS/Android) including auth, data and runtime protections.
• Secure APIs with OAuth, token-based auth, rate limiting and abuse prevention.
• Conduct threat modelling, design reviews and hands-on security reviews of mobile/backend systems.
• Collaborate with product managers and engineers to embed security in development processes.

Skills

Mobile security

API security

Threat modelling

Secure SDLC

Job description

Job Title: Senior Security Engineer – Mobile & Application Security

Duration: 12 months + extension (Permanent is also considered if preferred)

Location: UK - fully remote acceptable, hybrid much preferred

Industry: Leading financial technology company

They are looking for two Senior Security Engineers with strong experience in mobile application security to help improve security across mobile and backend platforms. You will work hands-on with engineering and product teams to identify, design and implement security controls throughout the development lifecycle.

Responsibilities

• Mobile application security across iOS and Android, including authentication and authorization mechanisms, secure data storage, runtime protections and hardening techniques.
• API security, including OAuth and token-based authentication, abuse prevention, rate limiting and business logic vulnerabilities.
• Conduct threat modelling, design reviews and hands-on security reviews of mobile and backend systems.
• Work closely with product managers and mobile/backend engineers to embed security into day-to-day development.

Requirements

• Proven experience as an Application Security Engineer, Product Security Engineer or Mobile Engineer with a strong focus on application security.
• Strong understanding of mobile-to-API interaction patterns and common attack vectors in modern mobile applications.
• Strong hands-on experience across mobile and API security.
• Ability to work hands-on and pragmatically with engineering teams.
• Experience with React Native internals is nice to have.