Application Security Engineer in London

About MoonPay

Hi, we're MoonPay. We're here to onboard the world to the decentralized economy by making digital money move as universally and effortlessly as the internet. Why? Because crypto, stablecoins and blockchain aren't just technologies. They're tools for global financial empowerment. They give people and businesses more control over their money, their digital assets, and their future, opening access to legacy financial systems that have been out of reach for many.

What we do

MoonPay is a unified payments platform for digital currency. We make it easy for anyone, anywhere, to buy, sell, swap and pay in digital currencies as easy as sending an email. That simplicity is intentional, our focus is reducing complexity so people can participate confidently, without needing to be crypto experts. We power the entire flow between fiat and crypto end to end, with compliance, identity checks, fraud prevention, and settlement all built in. This end-to-end approach reflects how we work internally: with accountability, rigor, and trust built into everything we ship.

Proven at scale

Trusted by over 30 million customers and over 500 ecosystem partners, our secure, enterprise-grade platform is driving mainstream crypto adoption worldwide. Behind those numbers are millions of real people and organizations relying on MoonPay every day. We collaborate with innovative brands and projects to build secure, scalable solutions for a blockchain-powered future. This is an opportunity to help shape systems, not just scale them. And we're committed to doing it right. Fully licensed in the U.S. and regulated across the UK, EU, Canada, and Australia, because trust and compliance are non-negotiable. But we're just getting started. We've launched a consumer app that makes crypto accessible, intuitive, and usable for everyone, and it's growing fast. We're iterating every day to make it the best it can be. If you believe financial freedom should be for everyone. If you believe in building a fairer, more open financial system - we want you with us. To build systems that benefit all, we need contributions from all, regardless of background. Come build the future of payments and the decentralized economy with MoonPay. Let's make financial freedom and autonomy the new normal.

Locations Supported: UK, US, Poland, Spain, Portugal

Relocation available: No

Work pattern: This role will be remote.

About the Opportunity

Our Product Security team is a dynamic blend of proactive defenders and inquisitive problem-solvers. We are dedicated to strengthening our systems through rigorous security reviews and hands‐on penetration testing, and we actively manage our Bug Bounty program to ensure timely validation, response, and remediation. We leverage cutting‐edge tools and techniques to build robust defenses, and collaboration is central to how we work; embedding security best practices throughout the SDLC. We continuously research emerging threats, develop effective mitigation strategies, and empower engineering teams through clear guidance and practical security training. We maintain up‐to‐date security standards and documentation, lead incident response efforts with precision, and are passionate about spreading a secure‐by‐design culture while contributing to the wider security community.

What You Will Do

• Conduct threat modelling reviews of Technical Design Documents (TDDs) for new and existing features, providing clear, actionable security recommendations early in the design process.
• Perform and support application security assessments, including penetration testing, vulnerability assessments, and proof‐of‐concept (PoC) development where appropriate.
• Investigate, triage, and respond to Bug Bounty program submissions, validating findings and working with engineering teams to drive timely remediation.
• Own and continuously improve application‐layer protections, including managing and tuning Cloudflare WAF and related security controls.
• Partner closely with engineering teams to embed security best practices throughout the SDLC, from design and development through deployment and maintenance.
• Research and track emerging threats and vulnerabilities, translating findings into practical mitigation strategies relevant to our technology stack.
• Develop and deliver security guidance, training, and awareness for engineering teams to raise the overall security maturity of the organization.
• Contribute to the creation, maintenance, and evolution of security standards, processes, and documentation.
• Participate in and eventually lead incident response activities, supporting investigation, containment, remediation, and post‐incident improvements.

About You

• You have developed a breadth of experience across multiple security domains, including web and mobile application security, infrastructure and cloud security, and can connect these areas to drive a holistic security approach.
• You have hands‐on experience performing white‐box, source code‐assisted web and mobile application penetration testing, from vulnerability discovery through triage and exploitation.
• You have the ability to read, understand, and review source code to identify security issues, with ideally, a particular focus on JavaScript and TypeScript codebases.
• You have a strong understanding of Threat Modelling principles and their practical application to the secure software development lifecycle (SDLC).
• You have experience working with web application firewalls to help protect applications, assess coverage, and support tuning rules to mitigate common attack patterns.
• You have experience embedding application security practices into CI/CD pipelines, enabling early detection of vulnerabilities and close collaboration with engineering teams throughout the development lifecycle.
• You have collaborated closely with engineering teams to clearly communicate security findings, explain vulnerabilities, attack paths, and mitigations, and support the implementation of effective fixes for both technical and non‐technical audiences.
• You are self‐motivated, proactive, and take strong ownership of your work, operating effectively in a remote environment while maintaining a collaborative, team‐focused mindset.

Nice‐to‐have experience:

• You have experience in JavaScript and TypeScript, including the ability to read, understand, and reason about modern web application codebases.
• You have experience working with Cloudflare, including its hosting and Web Application Firewall (WAF) capabilities, to help secure and operate internet‐facing applications.
• You have experience testing and securing GraphQL, REST APIs, including understanding common GraphQL/REST‐specific attack vectors and security considerations.
• You have experience or a strong interest in Web3 security testing, including assessing smart contracts, blockchain‐based applications, or Web3 integrations.
• You have an interest in agentic engineering, including emerging patterns in autonomous systems, tooling, or workflows, and their security implications.

Bonus Points

• You contribute or have contributed to the security community through open source involvement, participation in CTFs, or speaking at local information security meetups and conferences.
• Your background includes experience working with disruptive technologies and successfully launching products, ideally within FinTech, SaaS, or Crypto.
• You hold one or more security relevant certifications such as OSCP or OSWE.

Values

• B – Be Hungry
• L – Level Up
• O – Own It
• C – Crypto Curious
• K – Kaizen

Research has shown that women are less likely than men to apply for this role if they do not have experience in 100% of these areas. Please know that this list is indicative, and that we would still love to hear from you even if you feel that you are only a 75% match. Skills can be learnt, diversity cannot.

Benefits & Perks

• Competitive salary package
• Equity package: We believe financial freedom starts with our employees, so all employees have ownership at MoonPay.
• Pay for performance equity bonus: Those who drive outsized outcomes receive outsized rewards.
• Moonshot award. We honor exceptional impact – 10 employees twice a year, each earning a $250,000 equity grant.
• Unlimited holidays: We give you the autonomy to choose when to work (and when to switch off).
• Hybrid working schedule: Work fully remotely or your nearest Moonbase, the choice is yours.
• Private Healthcare benefits: To protect you and your loved ones.
• Enhanced parental leave: So you can spend more time with your loved ones without a second thought.
• Annual training budget: We support your training journey every step of the way.
• Home office setup allowance: Create the home office of your dreams.
• Remote working allowance: Those working fully remotely get a little extra for utilities.
• Monthly budget to spend on our products and zero‐fee crypto transactions: Cultivate your inner DEGEN.
• Employee referral programme: Great people know great people, refer them to receive 10K in USDC.
• Regular remote company offsites: Meet your colleagues regularly for high‐impact in‐person sessions and hackathons.
• Working in a disruptive and fast‐growing company where excellence is rewarded.

Commitment to Diversity

At MoonPay we believe that every voice matters. We strive to create a mindful and respectful environment where everyone can bring their authentic self to work, and experience a culture that is free of harassment, racism, and discrimination. That's why we are committed to diversity and inclusion in the workplace and are a proud equal opportunity employer. We prohibit discrimination and harassment of any kind based on race, color, religion, sex, sexual orientation, gender identity, national origin, age, disability, protected veteran status or any other characteristic protected by law. This policy applies to all employment practices within our organization, including, but not limited to, hiring, recruiting, promotion, termination, layoff, and leave of absence. MoonPay is also committed to providing reasonable accommodations in our job application procedures for qualified individuals with disabilities. Please inform our Talent Team if you need any assistance completing any forms or to otherwise participate in the application process. We may use artificial intelligence (AI) tools to support parts of the hiring process, such as reviewing applications, analyzing resumes, or assessing responses. These tools assist our recruitment team but do not replace human judgment. Final hiring decisions are ultimately made by humans. If you would like more information about how your data is processed, please contact us.