This is official Magic Actions for YouTube home website and it is 100% safe for everyone.
100% Safe and Clean - checked by Google, Siteadvisor and other website checkers: https://www.siteadvisor.com/sitereport.html?url=mycinema.pro
opens in a new tab or window to "update browser" and is potentially dangerous if you click on it.
The extension "magic actions for youtube" is what causes this to pop up and while the extension used to be good it is no longer since it has been doing this.