Offensive Security Engineer

About Finix

Finix is building the global operating system for fintech, starting with payments. From startups to publicly traded companies, Finix processes tens of billions of dollars annually both in-store and online. Finix was founded in 2015 and is headquartered in San Francisco. To date Finix has raised over $200M, including a $75M Series C led by Acrew Capital and Lightspeed Venture Partners and backed by American Express Ventures, Bain Capital Ventures, Homebrew, Inspired Capital, Visa, and others
About the Role: The Engineering organization at Finix owns the delivery and stability of our product end to end. As an Offensive Security Engineer, you will find weaknesses in Finix’s applications, cloud infrastructure, and corporate environment before attackers do, and work with engineers to fix them. You will run our internal penetration testing program and work closely with Engineering, Information Security, Compliance, and IT.
This is an in-office position based in our San Francisco office.

You Will:

• Plan and run red team tests across our web applications, APIs, AWS infrastructure, Kubernetes, and corporate environment
• Perform PCI DSS penetration testing and segmentation testing for our cardholder data environment as a Level 1 service provider
• Test new features and architecture changes, and partner with Engineering on threat modeling and secure design
• Review source code, especially Java services, for security flaws, and help engineers understand and fix them
• Run purple team exercises with detection and incident response to validate and improve our alerting
• Validate and reproduce bug bounty and third-party pentest findings, and assess their real-world impact
• Write clear reports with reproducible steps, business impact, and practical remediation guidance, and retest fixes
• Build tooling and automation to scale offensive testing and catch regressions
• Use frontier AI models to accelerate offensive testing, including building AI-assisted workflows and agents for recon, code review, vulnerability discovery, and exploit validation
• Deploy and operate self-hosted AI models for security testing, so source code, findings, and sensitive data stay inside Finix’s environment
• Test internal AI tooling and LLM integrations for prompt injection, data leakage, and abuse

You Have:

• 4+ years of hands-on offensive security experience, such as penetration testing, red teaming, or application security testing
• Deep web application and API testing skills
• Experience attacking cloud environments, especially AWS
• Proficiency in Python or Go, the ability to read and review Java code, and mastery with tools like Burp Suite
• Hands-on experience using frontier AI models in offensive security work, such as AI-assisted code review, fuzzing, or automated testing agents
• Strong ability to explain findings and risk to engineers and non-technical stakeholders
• Sound judgment and respect for scope and rules of engagement when testing production-adjacent systems

Nice to Have:

• Published CVEs, security research, conference talks, or recognition in bug bounty programs
• CTF experience
• Kubernetes and container security testing (EKS)
• Mobile or Android application testing
• Active Directory, Okta, or identity provider attack techniques
• Familiarity with payment systems, such as card networks, HSMs, or ISO 8583
• LLM and AI application security testing

----------------------------------------- Finix is an equal opportunity employer and values diversity. We do not discriminate on the basis of race, religion, color, national origin, gender, sexual orientation, age, marital status, veteran status, disability status, or any other protected class.
Role: Security Engineer
Level: IC4-IC5
Location: San Francisco, CA
Compensation Range: $180,000 - $230,000/year + Equity + Benefits Our salary ranges are determined by role, level, and location. The range displayed on each job posting reflects the minimum and maximum target for new hire salaries at our headquarters in San Francisco, California. Individual pay is determined by work location, job related skills, experience, and relevant education or training.