Security is a foundational requirement of any modern web application. Users expect their personal information to be safeguarded, organizations depend on compliance with regulations, and attackers are constantly probing for weaknesses. A single vulnerability can undermine trust, compromise sensitive data, and damage reputations that took years to build. For these reasons, security cannot be seen as an isolated phase or a checklist completed before deployment. It must be woven into the development lifecycle and integrated into the design of every component.