A Content Security Policy (CSP) can prevent XSS and other vulnerabilities by specifying allowed resources and their origins, defining directives to control specific elements of the policy, and gaining the ability to report policy violations to the server. A CSP makes it difficult for hackers to inject malicious code into a website's legitimate users, protecting against common web hacking tactics such as injection attacks and cookie theft. By implementing a CSP, developers can support other security best practices like template systems, vulnerability scanning, and manual security reviews, and improve their secure coding skills. Additionally, using a CSP is relatively easy and essential for websites involving complex web applications, login functionalities, and user cookies to stay secure against XSS vulnerabilities.