The fast integration of cloud computing has revolutionized the entire digital infrastructure but at the same time has created complicated security issues which erode trust, privacy and regulatory considerations. Conventional methods of cloud security tend to concentrate on single control mechanisms and this creates important lapses in multi-cloud and hybrid contexts. This study examines the modern cloud security issues, such as data breaches, insider threats, misconfigurations, and the emerging dangers of AI-driven and quantum-era threats and contributes to the development of a new Cloud Security Maturity Model (CSMM). The CSMM offers a stratified map which starts with the basic controls like identity and access management (IAM) and encryption, to the implementation of Zero Trust, dynamic AI-based defenses and quantum resistant governance. The research, based on IAM models (RBAC, ABAC, PBAC) technical analysis, network segmentation in zero-trust deployments, and automation in cloud-native security information and event management (SIEM) advances the insights on the practical barriers to implementation. The insights provided by cases, such as the Capital One breach in 2019, and the lessons learned by reading the Verizon DBIR and ENISA reports, suggest the presence of common vulnerabilities and provide an example of how an organization can move toward more resilient architecture. This publication is a contribution to both the literature and practice by incorporating empirical and visionary approaches to security, compliance, and resilience by providing a structured approach to the threat landscape that is likely to evolve over time in cloud ecosystems.