How to disable installing apps via desktop browser
Frankly, if someone has access to your logged-in account, they could do much more nefarious things than installing filling your phone with apps (such as accessing sensitive emails).

That being said, if you're particularly concerned about this:


Navigate to Google Play Settings on your desktop browser after signing in
Toggle the visibility of the device you want to prevent installations to




That's it. The downside of this is anyone could potentially reverse this setting, install apps and restore it without your knowledge. But you really shouldn't leave logged-in sessions around in the hands of people you don't trust.