Quantum computing is becoming increasingly widespread due to the potential and capabilities to solve complex problems beyond the scope of classical computers. As Quantum Cloud services are adopted by businesses and research groups, they allow for greater progress and application in many fields. However, the inherent vulnerabilities of these environments pose significant security concerns. This survey delivers a comprehensive analysis of the security challenges that emerged in quantum cloud systems, with a distinct focus on multi-tenant vulnerabilities and the classical-quantum interface. Key threats such as crosstalk attacks, quantum-specific side-channel vulnerabilities, and insider threats are all examined, as well as their effects on the confidentiality, integrity, and availability of quantum circuits. The design and implementation of various quantum architectures from quantum cloud providers are also discussed. In addition, this paper delves into emerging quantum security solutions and best practices to mitigate these risks. This survey offers insights into current research gaps and proposes future directions for secure and resilient quantum cloud infrastructures.