A bit off-topic, but does anybody have any examples of websites which use this dark pattern? I am interested in trying to disable this "feature" client-side for the sake of privacy.
Once you have entered your email address on a page with JS and the page has sent any additional network traffic, you have to assume that the server has your email address if they want it. JS is just too complex to offer any other guarantees.
You could disable JavaScript, otherwise there's no general way of preventing this type of behavior -- as far as I can imagine there are too many different ways of scooping up user input data to generally block via a browser add-on.
