CSP Directives Explained

Content Security Policy (CSP) is a security feature that helps prevent a variety of attacks, including Cross-Site Scripting (XSS) and data injection attacks. It allows web developers to control the sources from which content can be loaded on their web applications.

Implementing CSP can help to:

• Reduce the risk of XSS attacks
• Prevent data injection attacks
• Control resources that can be loaded on your site
• Establish a secure environment for your users

CSP directives define the policy for loading resources on your site. Here are some common directives:

• default-src: Serves as a fallback for other directives when they do not have a specified source.
• script-src: Specifies valid sources for JavaScript.
• style-src: Specifies valid sources for stylesheets.
• img-src: Specifies valid sources for images.
• connect-src: Limits the origins for fetch, XMLHttpRequest, and WebSocket connections.
• font-src: Specifies valid sources for fonts.
• object-src: Specifies valid sources for plugins like Flash.

Example of a CSP header:

Content-Security-Policy: default-src 'self'; script-src 'self' https://trusted-scripts.com;

To effectively implement CSP, consider the following best practices:

• Start with a report-only policy to identify issues.
• Use nonce or hash for inline scripts.
• Avoid using * (wildcard) for sources.
• Regularly review and update your policy.
• Monitor reports for violations.