Staff Application Security Engineer

pbThis 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 Belgium. /b /p pHelp 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. /p h3Accountabilities /h3 ul lipDesign 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. /p /li lipOwn 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. /p /li lipIntegrate 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. /p /li lipDevelop 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. /p /li lipBuild reusable security patterns, hardened libraries, and secure defaults for authentication, authorization, input validation, secrets management, and cryptographic operations. /p /li lipContribute directly to production codebases by implementing security fixes, developing security libraries, and building automation and CI integrations. /p /li lipLead threat modeling and architecture security reviews for new products, features, and significant technical changes across APIs, web and mobile SDKs, dashboards, and data pipelines. /p /li lipManage vulnerability identification, risk assessment, prioritization, and remediation for findings from security scanners, penetration tests, bug bounty reports, and customer disclosures. /p /li lipConduct 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. /p /li lipPay particular attention to adversarial threats involving fraud detection and bot mitigation, identifying weaknesses that could allow attackers to bypass or undermine platform protections. /p /li lipCollaborate with penetration testing and compliance specialists to scope assessments, validate fixes, retest findings, and translate technical discoveries into actionable engineering work. /p /li lipLead technical investigations of application-layer security incidents, coordinating containment, root‑cause analysis, remediation, and collaboration with cloud infrastructure teams when necessary. /p /li lipDefine application security logging and alerting requirements and partner with engineering and cloud platform teams to implement effective detection capabilities. /p /li lipSupport engineering teams through security consultations, office hours, secure coding guidance, and a Security Champions program that expands security expertise across the organization. /p /li lipDevelop practical secure coding training based on real application code, vulnerabilities, and lessons learned from security incidents. /p /li lipMentor engineers through code reviews and architecture feedback, helping improve security awareness and engineering quality without relying solely on mandates. /p /li lipPartner with application security leadership to shape technical priorities, communicate findings and risk assessments, and execute initiatives that advance the broader security roadmap. /p /li lipProvide technical evidence for security controls, contribute to vendor security assessments, and support enterprise customer due diligence, security questionnaires, architecture discussions, and penetration testing summaries. /p /li /ul h3Requirements /h3 ul lip