Hi @Pschwenk, while I concur that the new web app raises concerns, it isn’t as bad as you might think. Sonos servers are not able to “reach into” your home network; rather your Sonos devices connect to the Sonos servers in tandem with the web app and the new mobile apps connecting to the Sonos servers. I call this a “split architecture” and it is prevalent in almost all smart home device (thermostat, lighting, etcetera). Nothing needs to be opened in your firewall, which is one reason the split architecture is used so widely.
First thing I suggest is setting a proper strong password on your Sonos account. Go to https://www.sonos.com/en-us/myaccount/user/profile and click the “Reset password” link. Second thing I suggest is letting Sonos know that they need to implement two factor authentication (2FA) on sonos.com (and by extension, the web app).