Several news outlets reported on this yesterday.
Here’s the Forbes take:
iPhone users of Pokemon GO, beware: the app has access to your entire Google account. That’s a major problem for fans of the game. Shockingly, there’s no warning about the extensive permissions either. For now, it’s unclear if Android owners are affected, though reports of sporadic Google account access have emerged.
To be clear, the app, as it stands, can read and write emails. It can also view your Google Docs, search history and Maps use. And your private photos. It’ll also take data that’s standard for modern apps, like IP and email addresses. Given the app by necessity has to use location data, Niantic suddenly has access to incredibly private information of millions of individuals across the world.