Staff Application Security Engineer

This position is listed on behalf of a partner company, who manages all applications and next steps. Our partner is looking for a Staff Application Security Engineer based in Spain.
Help establish and scale a dedicated application security function within a high-growth technology environment where protecting customers against fraud and abuse is a core priority. As a senior individual contributor, you will combine deep security expertise with hands-on software engineering to identify vulnerabilities, strengthen development workflows, and build practical security tooling. You will design secure software development practices, lead threat modeling and security reviews, and drive vulnerability remediation across complex APIs, SDKs, and cloud-based systems. Working closely with engineering teams and security leadership, you will integrate AI-powered tools into security testing and remediation while maintaining rigorous quality standards. This role offers substantial technical autonomy, opportunities to influence engineering practices across the organization, and the chance to solve challenging security problems at scale. You will help make security an integral part of product development rather than a separate compliance requirement.
Accountabilities:
Design and implement a secure software development lifecycle (SDLC), incorporating security requirements, design-time threat modeling, secure code reviews, and pre-release testing into existing engineering workflows.
Own and improve application security tooling, including static and dynamic application security testing (SAST/DAST), software composition analysis (SCA), dependency scanning, secrets detection, and container and infrastructure-as-code scanning.
Integrate security tools into CI/CD pipelines, reduce false positives, establish clear vulnerability ownership and remediation service-level agreements (SLAs), and ensure findings lead to meaningful action.
Develop an AI-first security engineering approach using AI-assisted vulnerability triage, automated remediation, security review agents, and AI-augmented testing, with evidence-based controls governing what these tools can flag, block, or fix.
Build reusable security patterns, hardened libraries, and secure defaults for authentication, authorization, input validation, secrets management, and cryptographic operations.
Contribute directly to production codebases by implementing security fixes, developing security libraries, and building automation and CI integrations.
Lead threat modeling and architecture security reviews for new products, features, and significant technical changes across APIs, web and mobile SDKs, dashboards, and data pipelines.
Manage vulnerability identification, risk assessment, prioritization, and remediation for findings from security scanners, penetration tests, bug bounty reports, and customer disclosures.
Conduct hands-on security testing, including manual code review and exploitation testing for authentication and authorization weaknesses, API vulnerabilities, injection attacks, server-side request forgery (SSRF), business-logic flaws, and abuse scenarios.
Pay particular attention to adversarial threats involving fraud detection and bot mitigation, identifying weaknesses that could allow attackers to bypass or undermine platform protections.
Collaborate with penetration testing and compliance specialists to scope assessments, validate fixes, retest findings, and translate technical discoveries into actionable engineering work.
Lead technical investigations of application-layer security incidents, coordinating containment, root-cause analysis, remediation, and collaboration with cloud infrastructure teams when necessary.
Define application security logging and alerting requirements and partner with engineering and cloud platform teams to implement effective detection capabilities.
Support engineering teams through security consultations, office hours, secure coding guidance, and a Security Champions program that expands security expertise across the organization.
Develop practical secure coding training based on real application code, vulnerabilities, and lessons learned from security incidents.
Mentor engineers through code reviews and architecture feedback, helping improve security awareness and engineering quality without relying solely on mandates.
Partner with application security leadership to shape technical priorities, communicate findings and risk assessments, and execute initiatives that advance the broader security roadmap.
Provide technical evidence for security controls, contribute to vendor security assessments, and support enterprise customer due diligence, security questionnaires, architecture discussions, and penetration testing summaries.
Requirements:
The ideal candidate is an accomplished security engineer who combines strong software development skills with extensive practical application security experience. You should be comfortable independently driving complex initiatives, working directly within engineering repositories, and influencing technical decisions across teams. Required qualifications include:
At least 8 years of experience in software engineering and/or security engineering, including 5 or more years focused on application security.
Experience building or improving application security programs within a product engineering organization, with a strong emphasis on hands-on implementation rather than consulting or auditing alone.
Strong software engineering fundamentals and the ability to write production-quality code in TypeScript, JavaScript, Go, Python, or a comparable language.
Familiarity with modern web applications, APIs, software architectures, source code repositories, and CI/CD pipelines.
Deep practical application security expertise, including OWASP Top 10 and related vulnerabilities, authentication and authorization design, API security, injection attacks, SSRF, cryptographic misuse, business-logic flaws, and abuse scenarios.
Ability to identify vulnerabilities through manual testing, explain their real-world impact, and propose practical fixes that engineering teams can implement.
Demonstrated experience leading threat modeling and architecture security reviews for complex systems and producing threat models that inform engineering decisions.
Experience deploying, configuring, and tuning SAST, DAST, SCA, secrets detection, and related security tooling within CI/CD workflows.
Practical experience using AI-assisted security tools for code analysis, vulnerability triage, or automated remediation in real-world environments.
Regular use of AI agents in security work, with a clear understanding of their limitations, reliability, false-positive risks, and appropriate level of autonomy.
Experience owning vulnerability management processes, including triage, severity classification, remediation tracking, penetration testing follow-up, and enforcement of remediation SLAs.
Proven ability to influence engineering teams through technical credibility, effective collaboration, well-designed tools, and actionable guidance rather than formal authority alone.
Excellent written and verbal communication skills, including the ability to produce precise security findings and explain technical risks to engineers, leadership, and customer security teams.
Strong analytical skills, sound technical judgment, and the ability to work independently on ambiguous, multi-quarter initiatives.
Nice-to-have qualifications:
Experience in fraud detection, bot mitigation, identity security, or device intelligence.
Strong cloud security knowledge, particularly AWS IAM, network boundaries, secrets management, and workload identity.
Familiarity with cloud security posture management tools such as Wiz or equivalent solutions.
Experience securing client-side applications and mobile SDKs, including browser security, anti-tampering techniques, obfuscation tradeoffs, and iOS or Android SDK hardening.
Experience with multi-tenant SaaS platforms and high-volume, latency-sensitive APIs.
Experience operating a bug bounty program through platforms such as HackerOne, Bugcrowd, or equivalent services.
Awareness of AI and machine learning security risks, including prompt injection, LLM-integrated features, agent permissions, and model or data-pipeline vulnerabilities.
Experience with autonomous or AI-augmented penetration testing and attack simulation, including an understanding of how these approaches complement human-led testing.
Relevant security certifications, such as OSCP, OSWE, GWAPT, or CSSLP, or evidence of security research, published CVEs, or open-source security contributions.
Experience implementing or supporting SOC 2 or ISO ***** controls as the engineering owner responsible for making them operational.
Benefits:
Annual base salary ranging from $177,000 to $240,000, depending on location, experience, and expertise.
Location-based salary examples include $209,000-$240,000 for New York City and $177,000-$204,000 for Chicago.
Fully remote work environment, subject to geographic and regulatory restrictions.
Significant technical autonomy and the opportunity to shape the application security function from its early stages.
Executive-level support for application security initiatives and collaboration with dedicated security leadership.
Opportunity to focus on hands-on engineering, security tooling, vulnerability discovery, and remediation rather than primarily administrative compliance work.
Access to an established security technology environment that includes tools such as Snyk, Wiz, Cloudflare, and Okta.
Collaboration with cloud platform, engineering, and compliance specialists who treat security as a shared responsibility.
Opportunities to influence enterprise security practices and protect high-volume systems against sophisticated fraud and abuse threats.
An inclusive, globally distributed working environment that values diverse perspectives and professional contributions.
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