Content Security Policy (CSP)

Content Security Policy (CSP) is a security feature that helps prevent a variety of attacks such as Cross-Site Scripting (XSS) and data injection attacks. CSP allows web developers to define which resources can be loaded and executed on their web pages.

CSP is essential for securing web applications by:

• Mitigating XSS attacks by restricting script execution.
• Defining trusted sources for content, such as images, scripts, styles, and more.
• Reducing the risk of data theft and other client-side attacks.

To implement CSP, you can use the HTTP header or a meta tag. Here’s how to do it using both methods:

3.1 Using HTTP Header

Content-Security-Policy: default-src 'self'; script-src 'self' https://apis.example.com; img-src 'self' data: https:;
            

3.2 Using Meta Tag

<meta http-equiv="Content-Security-Policy" content="default-src 'self'; script-src 'self' https://apis.example.com;">
            

Follow these best practices when implementing CSP:

1. Start with a report-only policy to see what would be blocked without enforcing it.
2. Use specific directives like script-src and img-src instead of default-src.
3. Avoid using * (wildcard) in your policy; specify trusted domains instead.
4. Regularly review and update your CSP to adapt to changes in your application's architecture.