Macbook keeps deselecting currrent application

My Macbook keeps deselecting the current application. I first noticed it while I was using Chrome. But it also does it in, for example, Safari or Firefox. Every time I try to type into the address bar, I get less than a second before the application is deselected; it's really annoying. I tried rebooting the Macbook, disconnecting the wireless mouse, etc. I also tried logging the touchpad inputs, but it doesn't seem to register any gestures I didn't make.

Strangely enough; it doesn't seem to always do it. For example; it won't do it while I'm on the settings screen.

Does anyone have any ideas on how to diagnose this issue?