Occasionally some setting gets changed accidentally, such that when I move the cursor across the screen, every edge of every surface that it crosses gets highlighted in orange. If planes are visible, every edge of every plane that the cursor touches turns orange also.

To be precise, this happens whether I'm in a sketch or out of it. I can be viewing in wireframe, hidden lines visible, shaded with edges, whatever. And I'm not clicking on anything, just moving the cursor.

This is very annoying and distracting, and makes it hard to view or select anything. What the heck is going on here? How do I turn off this behavior?