Offensive Security Engineer

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

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

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

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