To manage authentication and authorization, use established libraries, implement JWT for secure sessions, and validate user permissions on each request.

Managing user authentication and authorization is crucial for the security of your web app. Start by using established libraries or frameworks that handle these processes, such as Passport.js for Node.js applications or Firebase Authentication for front-end frameworks. These libraries simplify the implementation of secure authentication methods and help protect against common vulnerabilities. For session management, consider implementing JSON Web Tokens (JWT). JWT allows you to encode user information and securely transmit it between the client and server. After a user logs in, generate a token that includes user details and expiration information, then send this token back to the client for subsequent requests. On each request, validate the token to ensure the user is authenticated. Additionally, implement role-based access control (RBAC) or similar authorization methods to manage user permissions effectively. Define roles within your application (e.g., admin, user, guest) and assign appropriate permissions to each role. On the server side, check user roles before processing requests to ensure that users can only access resources and perform actions they are authorized for. It's also essential to validate user inputs on both the client and server sides to protect against injection attacks. Consider implementing features such as password hashing (using bcrypt or similar libraries) and secure password recovery mechanisms to enhance user security. Regularly review and update your authentication and authorization strategies to adapt to new threats and ensure your web app remains secure.