Senior Offensive Security Engineer

In this role you will lead penetration testing efforts for Klarna’s internal and public systems, triage bug bounty submissions and external pentest findings, and propagate security insights across teams. You’ll analyze issues across the codebase and infrastructure, build tooling, and mentor engineers and SOC colleagues. The position sits on the Offensive Security team and centers on maturing Klarna’s security program. This is a hands-on, impact-driven opportunity in a fast-moving fintech environment.

• Run white-box and black-box penetration tests on internal and public-facing systems
• Manage triage and investigation of Bug Bounty submissions and external pentest findings
• Perform variant analysis to identify related issues across the codebase and infrastructure
• Assess security of third-party solutions and integrations
• Build tooling for reconnaissance, automation, and metrics collection
• Guide developers, product security teams, and SOC investigations with practical recommendations
• Lead demos, workshops, and training to spread offensive security practices
• Assess overall security of Klarna’s tech stack and contribute to maturing the security program

• 5+ years of conducting penetration tests and security assessments on production systems
• Ability to read code and identify vulnerabilities in Java and Node.js
• Experience with AWS and microservice architectures
• Clear, remediation-focused writing that translates findings into actionable steps
• Python scripting to develop own tooling
• Proactive, self-driven approach to advancing offensive security within the organization

• Clear written and verbal communication
• Initiative and self-motivation
• Collaboration across cross-functional teams
• Penetration testing and security assessments
• Java and Node.js code review
• AWS cloud security and microservices