Google updated their spam policies. They added "back button hijacking" to the list of malicious practices that can lead to spam actions. As long as your website isn't using a script to manipulate pages in a user's browser history and prevent the back button from doing what it should, you'll be fine.

> Notably, some instances of back button hijacking may originate from the site's included libraries or advertising platform. We encourage site owners to thoroughly review their technical implementation and remove or disable any code, imports or any configurations that are responsible for back button hijacking, to ensure a helpful and non-deceptive experience for users.