Recently a study from Princeton analysed what is called session replay. Oversimplified, it is a third party company acting as man in the middle between your PC and the website you are visiting, which then tracks and stores every mouseclick and keystroke to help the site owner analyse their website.
In order to do this, everything you type is not only stored at the website (like for example Evernote), but also on the servers of the analytics company. Obviously this poses a significant security issue. Or like one of the researchers from Princeton puts it: "Collection of page content by third-p