A cloud security assessment is an evaluation of the security of an organization's cloud-based systems and data, with the goal of identifying vulnerabilities or areas for improvement. It can be performed by an external third party or the organization itself. 

Typically, a cloud security assessment involves reviewing an organization's cloud environment and the controls and safeguards that are in place to protect it, such as data encryption, access controls, and network security measures. It may also involve testing the cloud environment to identify potential vulnerabilities, such as through penetration testing or vulnerability scanning. 

The results of a security assessment can be used to improve the security of a company's cloud environment. A cloud security assessment may be performed regularly to ensure that the organization's cloud security posture remains strong over time.