Senior Product Security Engineer (USA Only, 100% Remote)

About Us
Since 2013, we’ve been building a CRM that gets out of your way and helps your team sell more, faster. Now we’re building AI into every part of it, so Close does the busywork and your team does the selling. No manual data entry, no 10-click workflows. Just communication-first, AI-powered sales software designed to help you succeed and scale.
We're bootstrapped and profitable which means we answer to our customers and play by our rules. We're proud of our 120-person, 100% remote team, focused on building Close so that no small, scaling business fails because it can't figure out sales.

• Compensation: Competitive pay plus an organization-wide goal-based bonus

• Paid Time Off: ~5 weeks of PTO to start. Plus a 1-week all-company Winter Holiday Break and paid US holidays. You'll earn 2 extra days for every year you're with Close.

• 80% Work Option: Work with your manager to choose between a standard 5-day week or a 4-day week at 80% pay

• Parental Leave: Paid leave for primary and secondary caregivers

• Sabbatical: A 1-month paid sabbatical every 5 years with the team

• Healthcare (US residents): Two medical plans with Close covering 99% of your premium, plus Dental, Vision, HSA, FSA, and company-paid Long-Term Disability

• 401k (US residents): We match your contributions up to 6%, vested immediately

About the Role

Close is a CRM built around the communication tools sales teams use every day: email, calling, SMS, workflows, reporting, and AI. Underneath that product is a broad technical surface —Python services and a large application backend, a TypeScript and React frontend, public APIs, Docker and Kubernetes, AWS infrastructure, and integrations with providers that handle sensitive customer data.

Security work happens across it all today, but the ownership is spread across Engineering, Infrastructure, and Security & Trust. We’re hiring our first dedicated Product Security Engineer to make that work systematic. You’ll report to the Backend Platform team manager within EPD (Engineering, Product, and Design), while working across the entire product and infrastructure surface. You’ll find vulnerabilities, determine which findings matter most, and drive them through remediation. Often you’ll fix the problem yourself. Other times you’ll give the owning team a clear reproduction, a practical path forward, and enough context to prioritize correctly.

You’ll analyze code, build proof-of-concepts, test running applications, tune or replace noisy tools, and automate the repetitive parts of vulnerability management. This is not a role where you forward scanner alerts and call the queue managed. Product and application security will be your responsibility. You’ll partner closely with our Infrastructure team on cloud security, access, and secrets, and with our Security & Trust Lead on GRC Engineering, compliance (SOC 2) goals, audits, and corporate security.

This role is a new one at Close. You’ll have significant room to decide where better tooling, clearer ownership, and a small amount of code can reduce the most risk.

Our stack

Our backend is primarily Python, with Flask and FastAPI services and TaskTiger and Temporal handling much of our asynchronous work. We expose REST and GraphQL APIs and store data in MongoDB, PostgreSQL, Elasticsearch, and Redis.

Our frontend is a large single-page TypeScript application built primarily with React. We bundle with Vite, target modern browsers, and test with Vitest, React Testing Library, Playwright, and Chromatic. The product updates in near real time and uses technologies including WebSockets and WebRTC. Our mobile application is built with React Native.

We build and test Docker images in CI/CD and continuously deploy them to Kubernetes on AWS. Our infrastructure uses managed services including EKS, MSK, and ElastiCache, alongside services running on EC2. Terraform and Ansible automate much of the underlying infrastructure, and our containerized local development environment lets engineers run the full system on their own machines.

For this role, our stack extends beyond simply backend or frontend: browser behavior, frontend state, API authorization, asynchronous processing, data access, third-party integrations, containers, and cloud configuration can all be part of the same attack path.

We love open sourcing our code and ideas on our GitHub and on The Making of Close, our behind-the-scenes Product & Engineering blog. Check out our open source projects like SocketShark, TaskTiger, LimitLion and ciso8601.

AI is both how we build and what we ship, and that's reshaped what engineering looks like. This is a transformation we’re embracing and find deeply exciting.

You are

• An application security engineer who writes code. You can move from reading an unfamiliar code path, to reproducing an exploit, to proposing or shipping a production-quality fix. Strong Python or TypeScript experience would be especially useful; fluency across both backend and frontend systems is even better.

• Skilled at finding vulnerabilities conventional scanners may miss. You use modern AI-assisted review pipelines, guided by expert judgment, to uncover subtle flaws in web apps and APIs—from authentication, authorization, and tenant isolation to injection, SSRF, unsafe data flows, and business logic. You can threat-model designs, white-box review code, and test running systems.

• Offensive-minded and operationally responsible. You know how to test like an attacker without being careless with customer data or production systems. You can turn a finding into a safe reproduction, assess exploitability and business impact, and retest the eventual fix.

• An automation builder. You have worked with some mix of SAST, DAST, software composition analysis, container scanning, secrets scanning, or cloud posture tooling. More importantly, you know how to tune tools, connect them to engineering workflows, and remove noise.

• AI-native and accountable. You use coding agents and LLMs to accelerate investigation, code review, and repetitive engineering work, but you verify their output. You think carefully about what happens when agents clone untrusted code, install dependencies, or receive access to credentials.

• Able to separate severity from priority. A score is an input, not a forgone conclusion. You consider reachability, existing controls, customer impact, and attack chains, then explain the risk in language that is legible to an engineer or business owner.

• Comfortable working across the business. You’ll collaborate with product engineers, Site Reliability Engineers, Security & Trust Lead, auditors, and external researchers without confusing partnership for pass-off ownership. You will follow findings to closure even when another team is responsible for the fix.

• Self-directed in a remote environment. You can take an ambiguous surface (say, secret rotation or dependency remediation) and learn how it works across multiple systems then turn it into a practical plan with measurable progress.

You do not need to arrive as the deepest expert in every part of this scope. You do need to be able to investigate an unfamiliar system, determine what matters, and bring the right people with you.

You will

The work spans hands-on application security, security automation, vulnerability management, and infrastructure partnership. Depending on where you find the greatest risk and leverage, projects could include:

• Build a recurring product security review program. Threat model new features, audit high-risk areas, review code, and build safe proof-of-concepts in isolated development environments. Work across our backend, frontend, APIs, and customer-facing integrations.

• Improve application security testing. Combine static analysis, dependency and secrets scanning, dynamic testing in development, and carefully scoped production testing. Use existing tools where they fit and build focused automation where they don’t.

• Own vulnerability intake and remediation. Triage findings from HackerOne, scanners, penetration tests, audits, customers, and internal research. Reproduce issues, assess exploitability and impact, track remediation, and verify fixes. Serve as technical lead for our bug bounty program while contract and budget ownership remain elsewhere.

• Turn security alerts into useful engineering work. Verify scanner coverage and automate ingestion, deduplication, enrichment, prioritization, and routing—so teams spend less time interpreting alerts and more time fixing important issues.

• Make dependency remediation safer and less manual. Improve scanning across our Python and TypeScript codebases, then build workflows to assess upgrades, stage pull requests, run checks, and route work without exposing credentials to untrusted packages or build steps.

• Make secrets routinely rotatable. Partner with service owners and Infrastructure to inventory application secrets, add graceful rotation paths, document provider-specific runbooks, and automate rotation where the provider and risk justify it. Expand our use of Vault-backed dynamic credentials and reduce the number of rotations that require a coordinated fire drill.

• Strengthen AWS security with Infrastructure. Evaluate and improve automated detection of risky configuration across identity, networking, compute, storage, containers, and registries. Turn findings into secure defaults, just-in-time access patterns, infrastructure guardrails, and actionable remediation—not build a second Infrastructure team.

• Support audits and raising the security floor. Partner with Security & Trust on external assessments, provide technical context, and ensure findings are fixed rather than rediscovered. Along the way, create documentation, paved roads, and lightweight training that helps engineers make safer choices without waiting for a security review.

• Take a key technical role in security incident response. Partner with Engineering and Infrastructure to coordinate investigation, containment, and remediation. Contribute to root-cause analysis and follow-up improvements, translating lessons learned into stronger controls and reduced recurrence.

Tech you’ll touch: Python, TypeScript, React, Flask, FastAPI, GraphQL, Docker, Kubernetes, AWS, Vault, GitHub Actions, MongoDB, PostgreSQL, Redis, Kafka, Elasticsearch and the security tooling you help us choose.

Our Values

Build a house you want to live in - Examine long-term thinking and action

No BS - Practice transparency and honesty, especially when it’s hard

Invest in each other - Build successful relationships with your coworkers and customers

Discipline equals freedom - Keep your word to yourself and others

Strive for greatness - Constantly challenge yourself and others

Learn More

Listen to our CEO and Founder, Steli Efti, tell the story of Close’s journey in the $0-30m Blueprint .

Watch our culture video from our 2023 team retreat in Milan. Every year our entire team gathers in person to build connection, foster cross-functional collaboration, and have fun. In 2027, we're headed to Dusseldorf, Germany!

Explore our product. Check out a demo!

Our Hiring Process

We ask a few role-specific questions as part of our application process. These questions are designed to help us learn more about you from the start, so please answer each one thoughtfully. We see this as an opportunity to get to know you beyond your resume.

We use AI tools daily at Close and expect candidates to do the same. In evaluating your application, we aim to get a sense for you - the way you think, how you communicate, the work you've done. Applications that read as fully AI-generated will not be considered.

Regardless of fit, you can expect to hear back from our team with an update on the status of your candidacy.

If you progress to the interview process, you'll receive a full outline of the role-specific steps in your first touchpoint with us. We do our best to make the hiring process clear and human.