Content Security Policy (CSP)

Content Security Policy (CSP) is a feature that helps to prevent or minimize the risk of certain types of security threats. It consists of a series of instructions from a website to a browser, which instruct the browser to place restrictions on the things that the code comprising the site is allowed to do.

The primary use case for CSP is to control which resources, in particular JavaScript resources, a document is allowed to load. This is mainly used as a defense against cross-site scripting (XSS) attacks, in which an attacker is able to inject malicious code into the victim’s site.

A CSP can have other purposes as well, including defending against clickjacking and helping to ensure that a site’s pages will be loaded over HTTPS.

Source: https://developer.mozilla.org/en-US/docs/Web/HTTP/CSP