Senior Application Security Engineer

Role Overview

• 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.

Requirements

• 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.

Tech Stack

• Cloud
• Firewalls
• GraphQL
• JavaScript
• SDLC
• TypeScript
• Web3

Benefits

• 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