google/mantis

CyberStrike is an open-source AI-powered security testing platform that acts like a virtual red team — automatically probing your systems for vulnerabilities the way a human hacker would, but at machine speed and scale. You connect it to any major AI service like ChatGPT or Claude, and it deploys over a dozen specialized AI agents armed with thousands of pre-built attack techniques to find weaknesses across websites, cloud infrastructure, and software systems.

why it matters: As AI dramatically lowers the cost of cyberattacks, companies that can't afford large security teams are increasingly exposed — and tools like this democratize access to enterprise-grade security testing for any builder or startup. With nearly 1,800 stars and 740 contributors, this is gaining real traction as a category-defining open-source alternative to expensive penetration testing services that can cost tens of thousands of dollars per engagement.

OpenSSL is the world's most widely used open-source toolkit for securing internet communications — it's the engine behind the padlock icon you see in your browser, protecting data as it travels between apps and servers. It also includes a Swiss Army knife command-line tool for handling everything from creating security certificates to encrypting files.

why it matters: With over 30,000 stars and 1,400+ contributors, OpenSSL is foundational infrastructure that nearly every internet product quietly depends on — understanding it matters because any app handling sensitive data, payments, or user accounts is almost certainly built on top of it. For builders and investors, this project represents the kind of critical shared infrastructure where vulnerabilities (like the famous Heartbleed bug) can affect millions of products overnight, making it essential to track for risk and compliance reasons.

OWASP Nest is a discovery platform that helps people find, explore, and contribute to OWASP — the world's leading nonprofit focused on software security standards and best practices. Think of it as a curated directory and community hub that makes it easier to navigate OWASP's hundreds of projects, local chapters, and volunteer opportunities, all in one place.

why it matters: With 170 contributors and nearly 400 stars, this project signals strong community momentum around making security knowledge more accessible — a growing priority as regulators and enterprises demand better software security practices. For founders and PMs, it represents a ready-made engagement layer for the security community, and its open, contributor-friendly model demonstrates how open-source platforms can scale without a large core team.

Nuclei Templates is a large, community-built library of pre-written security checks that work with the Nuclei scanning tool to automatically detect vulnerabilities in websites and applications. Think of it as a crowdsourced rulebook that tells an automated security scanner exactly what to look for — from known software weaknesses to misconfigurations — so teams can quickly audit their products without manually searching for every possible flaw.

why it matters: With over 12,000 stars and 1,265 contributors, this project signals that automated security scanning is becoming a standard part of how software teams ship products, not an afterthought. For founders and PMs, this means security testing is increasingly accessible and affordable, raising the bar for what customers and investors will expect in terms of baseline product safety.