The document discusses common issues with broken authentication and authorization in web applications. It provides several case studies of authentication bypass vulnerabilities, including misusing authentication tokens, cookie manipulation, failing to invalidate sessions after password resets, and account takeover through password reset functionality. It also examines cases of broken authorization and privilege escalation, such as updating boolean or role-based privileges, bypassing client-side checks, directly accessing privileged pages, allowing low-privileged users to perform privileged actions, and deleting resources through IDOR. Remediation strategies are proposed, such as strengthening authentication tokens and sessions, implementing server-side access controls, and preventing debugging information leaks.