Senior Offensive Security Engineer - Penetration Testing

Klarna; Warszawa; On-site; PLN 370,000 - 479,000; Full time

Job summary

Klarna is seeking an experienced Offensive Security professional to run penetration tests and triage bug bounty findings across internal and public systems. You will analyze variants, assess third-party security and build tooling while guiding developers and SOC teams with practical remediation steps.

The role emphasizes hands-on security across Klarna's stack (Java/Node.js, AWS, microservices) and may involve training and demonstrations to spread best practices.

Qualifications

• 5+ years running penetration tests and security assessments on production systems.
• Able to read code and find vulnerabilities in Java and Node.js.
• Experience operating in AWS and reviewing microservice architectures for security gaps.
• Ability to write clear remediation steps for developers.
• Skilled in scripting with Python rather than relying on off-the-shelf scanners.
• Proactive in advancing offensive security at Klarna.

Responsibilities

• Run white-box and black-box penetration tests against internal systems and public-facing applications.
• Manage, triage, and investigate Bug Bounty submissions and external pentest findings.
• Perform variant analysis across codebase and infrastructure to identify related issues.
• Research and assess the security of third-party solutions and integrations.
• Build tooling for reconnaissance, automation, and metrics collection.
• Guide developers, product security teams, and SOC investigations with hands-on expertise.
• Run demos, workshops, and training that spread offensive security practices.
• Assess the security of Klarna's tech stack and help mature the security program.

Skills

Penetration testing

Code reading

AWS familiarity

Python scripting

Vulnerability assessment

Tools

Python

Job description

Klarna is seeking an experienced Offensive Security professional to run penetration tests and triage bug bounty findings across internal and public systems. You will analyze variants, assess third-party security and build tooling while guiding developers and SOC teams with practical remediation steps.

The role emphasizes hands-on security across Klarna's stack (Java/Node.js, AWS, microservices) and may involve training and demonstrations to spread best practices.