Content Security Policy (CSP) is a security feature implemented by web browsers that prevents attacks such as cross-site scripting (XSS) and data injection attacks by giving web application developers control over the resources a web page can load and execute.
CSP is implemented via an HTTP header that is sent to the client in the server's response. The header specifies a set of rules that the browser should enforce when loading resources for the page. The rules can be very specific, so that only certain domains or only certain types of resources can be loaded.
CSP can be a very effective way to reduce the risk of client-side attacks, but it can also be difficult to implement properly. It is important to test the policy carefully to ensure that it does not affect the functionality of the web application.