I has been confirmed by Google that there has been a major quality update performed. The update took place throughout a period of one week, but the peak was detected around August 1st and 2nd. A lot of websites were strongly affected. As for now, Google recommends not to take any sudden moves and just keep being focused on "building great content".
Google announced that the long-awaited Mobile-First Index has been launched. The process of migrating sites that follow the best practices for mobile has started, but it's not said how long the process will take.
Google sends out notifications to the site owners via Google Search Console.
Lear more here.
On the 14th of March Google started a week-long experiment of removing the organic results for the searches that can be answered definitively. Instead, a "Show all results" button was added. Many sources read it as an important signal of what Google intents to do in the future.