Senior Security Engineer - xStocks

As a Senior Security Engineer for xStocks at Payward, you own security end to end for a platform that brings real-world assets on-chain as tokenized securities across EVM, Solana, TON, Tron, and more. You are both an engineer and a security specialist: you ship products alongside the engineering team when the security queue is quiet, and you own security work end to end when it lands. You report into engineering and partner closely with the Payward security, CISO, and compliance functions.

What you'll do

• Own security deliverables end to end: coordinate and review smart-contract audits, respond to security questionnaires and due-diligence requests, support CISO and compliance initiatives, and drive findings into tracked, closed-out fixes.
• Run offensive assessments against xStocks platforms: pentest the web apps, APIs, backend services, and on-chain components, and build tooling to do it repeatedly rather than once.
• Continuously assess security posture by threat-modeling new and existing systems, reviewing architecture and key-management flows, and maintaining a living view of risks and their mitigations.
• Review code for security as a default reviewer on changes touching auth, cryptography, custody, signing, and fund movement across chains.
• Harden the platform by improving secrets handling, IAM and least-privilege, dependency and supply-chain hygiene, and detection and logging for security-relevant events.
• Secure custody and signing workflows by reviewing and hardening transaction signing flows, MPC and HSM integrations, signer permissions, admin roles, approval policies, and break-glass procedures.
• Contribute to product engineering by picking up regular backlog work in TypeScript to stay close to the codebase you defend.
• Support incidents by helping with detection, triage, response, and post-mortems, and feeding lessons back into the program.

What you bring

• An engineering foundation: you write and review production code comfortably in TypeScript and Node.js, and understand systems deeply enough to break them.
• Strong application and infrastructure security fundamentals in the OWASP landscape, authn and authz, injection, SSRF, supply-chain risk, and secure design, with real offensive work in pentesting, vuln research, or red-team.
• Applied cryptography and blockchain security knowledge: symmetric and asymmetric primitives, hashing, signatures, and key management, plus the security model of EVM, Solana, and ideally TON or Tron. You can read a smart contract and reason about how it fails.
• Ownership: you can take an ambiguous security item, an audit, a questionnaire, or an incident, and drive it to closure without being managed through it.
• Clear communication: you can explain a risk to engineers, to a CISO, and to an auditor, tailored to each audience.
• An automation instinct: you turn findings into tests, alerts, controls, documentation, or platform improvements rather than catching the same issue manually twice.
• Risk judgment: you can tell a theoretical issue from a material one, and communicate severity, likelihood, impact, and remediation tradeoffs clearly.

Nice to have

• Experience commissioning or remediating third-party smart-contract audits.
• Familiarity with custody and signing infrastructure such as HSMs, MPC, and ForDefi-style providers, and with on-chain transaction security.
• Cloud security depth in GCP or AWS, IAM, and container and runtime hardening.
• Detection engineering and security observability, including SIEM and log-based detections.
• Relevant certifications such as OSCP, OSWE, or GWAPT.
• Prior work in a regulated fintech or tokenization/DeFi environment.

About Payward

Payward, the parent company behind Kraken, NinjaTrader, Breakout, xStocks, Payward Services and CF Benchmarks, has spent the last 15 years building one of the most modern and globally accessible financial infrastructure platforms in the industry to advance an open, global financial system.