A blank box appears, that is, hold down the left (right) key and drag the mouse, and a box will appear, through which you can make a selection.

You can try what I said on other computers.

If this happens when the mouse is not connected, it means that the right (left) key on the touchpad of the notebook computer is stuck.

If you are a desktop, the left (or right) mouse button is stuck or shorted.

It is suggested to replace the mouse, or check the two buttons on the touchpad of the notebook to see if it pops up. If it pops up, it means a short circuit. Just send it to the maintenance point for cleaning.