Ever since 4.20, when I complete a game and return to the client my desktop is littered with 6-7 untitled folders, and my system preferences panel is open. This is occurring after every game. It seems like League is not disabling system hotkeys when active, although I'm scratching my head as to what keybinding is triggering it. Cmd-N is for a new folder, and I'm definitely not hitting that combination.
There is definitely a change in how League is treated as a window. I will occasionally hit spells and hear the system error tone, and the spell does not trigger. Hitting ESC resets this. In any event key presses in-game are triggering events in the desktop background.
This is happening in OS 10.9.5