With cookies and browser access, they could get into my emails, family photos, bank accounts, and even read desktop notifications from my phone's SMSs.
For developers, the real risk lies in the variety of dependencies our apps have, which could get compromised.
So, this isn't really news. There are also tools to access all your iMessage history from a Mac, for example.
I believe the feature is really useful, and for sure you can turn it off.