Content Security Policy

https://web.dev/csp/ (before was https://developers.google.com/web/fundamentals/security/csp)

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

https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy

https://infosec.mozilla.org/guidelines/web_security.html#content-security-policy