Senior Security Engineer (Offensive)

At Offchain, we aren’t just building products: we’re leading a movement.

As pioneers in blockchain scalability and security, we're at the forefront of transforming how the world interacts with decentralized applications. We're laying the foundation that will define the next generation of digital commerce, governance, and human interaction. This involves tackling real-world challenges that come with scaling blockchain technology, without compromising on its core principles: decentralization, security and transparency.

At the center of this vision is our people. Our team is made up of thinkers and doers that embrace new challenges and seek solutions that push existing boundaries. If you’re energized by solving unprecedented problems, and believe in the role that decentralized systems will play in creating a more equitable digital future, then we want to hear from you.

Why Offchain?

Offchain is setting the pace for the entire Ethereum ecosystem. We built the Arbitrum stack that powers Arbitrum One, the most widely adopted Ethereum scaling solution that exists today.

Arbitrum’s ecosystem is undergoing tremendous growth with hundreds of projects and dApps on Arbitrum One today. Over 100 different teams have used Offchain technology to build their own Arbitrum chains. Major players in the space, Robinhood, BlackRock, Ethena Labs, Securitize, Aave, and Apechain are all using the Arbitrum stack.

Arbitrum’s thriving ecosystem wouldn’t exist without our advanced technology stack. Arbitrum, Prysm, ZeroDev. These aren’t just product names. These are tools that are actively reshaping what's possible on Ethereum and advancing its core infrastructure.

To top it all off? We’re backed by $124 million in funding. We’ve demonstrated consistent execution with billions in secured value, thousands of supported projects, and infrastructure processing millions of transactions seamlessly.

The Role

• As a Security Engineer at Offchain, you will emulate the real-world tactics, techniques, and procedures of sophisticated adversaries to surface vulnerabilities across our infrastructure and ecosystem tools.

• You’ll run hands-on penetration tests, lead red team exercises, and work side-by-side with blue team partners to test, refine, and strengthen detection and response capabilities.

• Your efforts will directly shape how Offchain designs, launches, protects, and achieves compliance for the infrastructure that powers millions of users and applications - including key standards such as SOC 2.

What you'll do:

• Conduct comprehensive code audits across a variety of internal applications and infrastructure.

• Conduct comprehensive penetration tests across cloud environments (AWS), infrastructure, and backend applications.

• Collaborate with detection engineering, threat intelligence, and incident response groups to review security controls, uncover coverage gaps, and enhance overall detection quality.

• Build, maintain, and evolve custom offensive tools, scripts, and automation frameworks to increase assessment speed.

• Offer offensive security expertise during incident investigations, including log analysis and root cause reviews.

• Keep up with evolving threats, vulnerabilities, and attack methods; share research internally and engage with the wider security community.

• Own offensive security projects from start to finish, mentor junior team members, and cultivate a culture of ongoing learning and knowledge exchange.

What you'll need:

• 5+ years of experience in offensive security, penetration testing, red teaming, or a closely related field.

• Extensive experience with conducting code audits to identify and remediate security issues.

• Experience with binary exploitation.

• Mastery of AWS & specific attack techniques and configuration weaknesses.

• Strong understanding of adversary tactics and frameworks like MITRE ATT&CK.

• In-depth knowledge of web application security, including OWASP Top 10, ASVS, and common vulnerability categories.

• Proficiency using offensive security tools such as Burp Suite, nuclei and similar frameworks.

• Strong programming skills in Python, Go, or similar languages, with proven experience developing tools or automation.

• Excellent written and verbal communication skills, with the ability to present complex technical details as clear, risk-focused recommendations.

• A natural ability to think like an attacker - creative, determined, and skilled at assessing risk across complex systems.

Nice-to-haves

• Web3 / blockchain security exposure: smart contract auditing, bug bounty hunting (e.g., Immunefi, Code4rena), or DeFi protocol review.

• Familiarity with Ethereum L1 / L2 node architecture and security risks.

• Experience in blockchain infrastructure penetration testing.