Senior Security Engineer

Senior Security Engineers & CISOs (Spain), we want to hear from you
Ledn is a global financial services company built for digital assets, helping to improve the everyday lives of Bitcoin holders while building generational wealth for the future. We offer a suite of egalitarian lending, savings and trading products to digital asset holders in over 120 countries around the world. Through our products & services, we can make a difference in the lives and futures of our clients - in real terms.
Our team at Ledn is a passionate group of individuals from diverse backgrounds. What we all have in common is an unshakeable conviction that digital assets can democratize access to the global economy and Ledn’s suite of products & services can play a critical role in doing so. The core values that guide us are: act with integrity always, own it, have a passion for progress, and lead with empathy. Combining these values with our conviction make Ledn an unstoppable force in changing the world for the better. Come join us as we build, innovate and revolutionize financial services
The Opportunity:
As a full-time Senior Security Engineer & CISO(Spain) , you will be a hands‑on, high‑ownership individual contributor responsible for strengthening Ledn's product, cloud, and software delivery security. You will find
vulnerabilities before attackers do, build controls that prevent entire classes of issues from reaching
production, and help engineers ship securely.
This is a builder-and-breaker role: you will assess our applications, APIs, AWS environment, Cloudflare
edge, and GitHub workflows from an adversary's perspective, then partner with owners to remediate
findings and validate the fixes. You will turn lessons from individual issues into practical standards,
automation, and measurable improvements.
You’ll work closely with Software Engineering, DevOps & Infrastructure, Risk, and Compliance. In a
regulated digital-asset environment, you will contribute technical controls, evidence, and incident
readiness that support Ledn's security and regulatory obligations
This is a unique, dual-mandate role based in Spain. Alongside the hands‑on security engineering work above, you will also serve as the Ledn Spain entity’s Chief Information Security Officer (CISO), operating within the second line of defense. In that capacity, you will own the local Information Security Framework and ICT Risk Register, report periodically to the Board on information security and ICT risk, and act as the primary point of contact for the CNMV and external auditors on cybersecurity and DORA matters.
About The Role:
Senior Security Engineer Core Responsibilities:
Secure Design & Threat Modeling Lead security reviews for new designs and existing features, translating threats into concrete engineering requirements before code reaches production.
Penetration Testing Plan and execute hands‑on testing of web applications, APIs, mobile‑facing services, and infrastructure; document reproducible findings, validate remediation, and coordinate independent assessments where needed.
Adversarial Validation Run red‑team and purple‑team exercises around realistic attack paths, then work with defenders to improve preventive controls, telemetry, detections, and response playbooks.
Secure Pull Requests Define a risk‑based security standard for pull requests, including review requirements and tuned merge gates for secret scanning, SAST, dependency review, and sensitive‑code ownership.
Product & API Security Review production code and architecture for vulnerabilities in authentication, authorization, session handling, data protection, and business logic; help teams address root causes rather than isolated symptoms.
AWS Security Assess and harden our multi‑