Senior Security Engineer - xStocks

Electric Capital; Brasil; On-site; BRL 180,000 - 300,000; Full time

Job summary

Payward is seeking a security-focused engineer to own security deliverables end-to-end across our platforms, from audits to fixes. You will pentest web apps, APIs, backends, and on-chain components, building reusable tooling and driving risk-based decisions.

You will work with engineers, CISOs, and compliance to harden the platform, improve identity and access controls, and advance secure-by-design practices in our tokenized finance stack.

Qualifications

• Must be an engineer-first security professional with production coding experience.
• Strong application and infrastructure security fundamentals.
• Applied cryptography and blockchain security knowledge.
• Ownership of a security item from audit to closure.
• Clear communication with engineers, CISO, and auditors.
• Automation mindset to turn findings into tests or controls.
• Ability to assess risk and communicate severity and remediation tradeoffs.

Responsibilities

• Own security deliverables end to end: audits, questionnaires, and fixes.
• Pentest web apps, APIs, backends, and on-chain components; build reusable tooling.
• Continuously assess posture; model threats and key-management flows.
• Review code for security; act as reviewer on auth, cryptography, custody, signing, and funds moves.
• Harden platform: secrets handling, IAM, least-privilege, supply-chain hygiene.
• Secure custody and signing workflows: MPC, HSM, signer permissions, admin roles.
• Contribute to product engineering; do backlog work in TypeScript.
• Assist incidents: detection, triage, response, and post-mortems.

Tools

TypeScript

Node.js

Job description

Building the Future of Open Finance

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, built to advance an open, global financial system.

The team

xStocks brings real-world assets on-chain as tokenized securities that are regulated, fully-backed, and tradable across multiple blockchains. Built within Payward, the xStocks team runs the infrastructure that issues, custodies, and settles these instruments across EVM, Solana, TON, Tron, and more. The platform moves real value, so security is not a feature bolted on at the end. It is a property of everything the team ships. This is a hybrid engineering and security seat built for someone who is genuinely both: 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.

The opportunity

• 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 turn findings into tracked, closed-out fixes.

• Run offensive assessments against our own platforms. Pentest the web apps, APIs, backend services, and on-chain components, and build the tooling to do it repeatedly rather than once.

• Continuously assess posture. Threat-model new and existing systems, review architecture and key-management flows, and maintain a living view of the risks and their mitigations.

• Review code for security. Be a default reviewer on changes touching auth, cryptography, custody, signing, and fund movement across our chains.

• Harden the platform. Improve secrets handling, IAM and least-privilege, dependency and supply-chain hygiene, and detection and logging for security-relevant events.

• Secure custody and signing workflows. Review and harden transaction signing flows, MPC and HSM integrations, signer permissions, admin roles, approval policies, and break-glass procedures.

• Contribute to product engineering. Pick up regular backlog work in TypeScript so you stay close to the codebase you are defending.

• Support incidents. Help with detection, triage, response, and post-mortems, and feed the lessons back into the program.

What you bring

• An engineer first. You write and review production code comfortably, TypeScript and Node.js in our stack, and you understand systems deeply enough to break them.

• Strong application and infrastructure security fundamentals. The OWASP-class vulnerability landscape, authn and authz, injection, SSRF, supply-chain risk, and secure design. You have done real offensive work in pentesting, vuln research, or red-team.

• Applied cryptography and blockchain security. 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, and tailor the message to each.

• An automation instinct. You do not want to catch the same issue manually twice, so you turn findings into tests, alerts, controls, documentation, or platform improvements.

• 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.

Unless a specific application deadline is stated in the job posting, applications are accepted on an ongoing basis.

Please note, applicants are permitted to redact or remove information on their resume that identifies age, date of birth, or dates of attendance at or graduation from an educational institution.

We consider qualified applicants with criminal histories for employment on our team, assessing candidates in a manner consistent with the requirements of the San Francisco Fair Chance Ordinance.

Our commitment

Payward is powered by people from around the world and we celebrate the diverse talents, backgrounds, contributions, and unique perspectives that everyone brings to the table. We hire based on merit, seeking out people with the right abilities, knowledge, and skills for the job. We encourage you to apply for roles where you don't fully meet the listed requirements, especially if you're passionate or knowledgeable about crypto.

We may ask candidates to complete job-related skills or work-style assessments as part of our hiring process. These assessments evaluate competencies relevant to the role and are applied consistently across candidates for similar positions. Results are considered alongside experience and interviews, and are not the sole basis for any employment decision.

As an equal opportunity employer, we don't tolerate discrimination or harassment of any kind, whether based on race, ethnicity, age, gender identity, citizenship, religion, sexual orientation, disability, pregnancy, veteran status, or any other protected characteristic as outlined by federal, state, or local laws.

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