OWASP (Open Web Application Security Project) is an open-source foundation providing authoritative resources, tools, and standards for web application security. Founded in 2001, it publishes the OWASP Top 10, a consensus document identifying the most critical security risks to web applications, updated regularly based on real-world data from thousands of organizations. The framework extends beyond web apps to include APIs, mobile applications, and modern software architectures. Understanding OWASP isn't just about memorizing vulnerabilities—it's about recognizing that security failures cluster around a few core patterns: trusting user input without validation, mismanaging authentication state, exposing sensitive data, and failing to design security into the application from the start. Modern applications face an expanded threat landscape including supply chain attacks and CI/CD pipeline compromises, making proactive security practices essential rather than optional.