CSPNet

CSPNet, or Content Security Policy Network, is a web security standard introduced to prevent a variety of attacks, including Cross-Site Scripting (XSS) and data injection attacks. It allows web developers to control resources the user agent is allowed to load for a given page. With CSP, a web application can whitelist sources of executable scripts, thus preventing the browser from loading malicious scripts.

The policy is defined using HTTP headers. It can specify valid sources for content types like scripts, stylesheets, images, fonts, objects, media, and child frames. For example, a policy might allow scripts to be loaded only from the same origin or specific trusted domains.

CSPNet can be enforced in two modes: report-only and enforce. In report-only mode, the browser will not block any resources but will send a report to a specified URI about the violations. This mode is useful for testing and debugging. In enforce mode, the browser will block any resources that do not comply with the policy.

CSPNet also supports a feature called "nonce" and "hash" to allow inline scripts and styles. Nonce is a unique, random value that is included in the policy and the script tag. Hash is a cryptographic hash of the script or style. These features provide a way to use inline scripts and styles without compromising security.

CSPNet is supported by all major browsers and is considered a best practice for web security. It is recommended to implement CSPNet for all web applications to protect against a wide range of attacks.