Deselecting anything forces box selection on Firefox

Using Firefox browser, any time I deselect an object in Figma (frames, images, etc), a gray box that says “paste” appears next to my cursor and moving the mouse automatically triggers a box-select (as if I were holding and dragging the mouse). I have to press Esc to make the “paste” box go away and click somewhere without selecting anything to make the box-select go away. This happens any time I deselect anything. This means that if I accidentally select something using the bug-induced box-select, it loops me back into the bug. It is hugely obtrusive to getting any work done.