Senior Offensive Security Engineer

Overview

In this role you will lead and perform penetration testing across Klarna’s internal and public systems, integrating bug bounty insights into the security program. You’ll work on a fast-moving offensive security team, covering code, infrastructure, and third-party integrations in a Java/Node.js/AWS environment. You’ll translate findings into actionable remediation and help elevate security across cross-functional teams. This is a hands-on, problem-solving position with a strong impact on product safety and incident readiness.

Responsibilities

• Run white-box and black-box penetration tests on internal systems and public-facing apps
• Triage, investigate, and validate Bug Bounty submissions and external pentest findings
• Perform variant analysis to locate related vulnerabilities across code and infrastructure
• Assess security of third-party solutions and integrations
• Build tooling for reconnaissance, automation, and metrics collection
• Guide developers, product security, and SOC investigations with concrete remediation steps
• Lead demos, workshops, and training to spread offensive security practices
• Assess and contribute to maturing Klarna's security program and tech stack security posture

Key requirements

• 5+ years of practical penetration testing and security assessments on production systems
• Proficient in reading code and finding vulnerabilities in Java and Node.js
• Experience with AWS and microservice architectures
• Clear, remediation-focused vulnerability reports with actionable steps
• Python scripting for tooling and automation
• Self-motivated with initiative to advance offensive security beyond tickets

• Strong communication and collaboration
• Proactive problem-solving mindset
• Ability to lead training and share knowledge across teams
• Penetration testing (white-box/black-box)
• Java and Node.js security
• AWS security and cloud native architectures

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