How can a lack of CSP harm a website?

Let's say you have a website where you advertise to users and earn money honestly. And everything is going well until users whose browsers are infected start visiting you. An infected browser will replace the advertising on your site with its own and show it to the user. The result: Pessimism on the part of search engines and a drop in revenue. If you implement a CSP policy on your site, other people's ads will no longer be presented to the end user, because the server from which the ad will try to load is not whitelisted. So now everything will be fine!

The application allowed us to configure a CSP security policy for the website, for the store, the blog, the hub. The W3C is now with the Content Security Policy Level 2 specification.

Application features: Control of the sources of styles, scripts, images, fonts, video and audio files, etc. on the site. 

Control over the sending of data to other sites, including logins and passwords by analyzing the reports of blocking of this or that resource, We can detect malicious code on the pages that has been introduced by attackers  ;)

The application does not make any changes to the html code, (index.html), but only generates a header transmitted by the server to the browser.

Thank you to Russia (the strength of the web) for allowing me to protect my work with the best technologies!