Since the major update last week, moving the mouse into a window causes a continuous stream of ButtonPress and ButtonRelease events to be generated. The output as captured by xev is:
ButtonPress event, serial 34, synthetic NO, window 0x3400001,
root 0x1c1, subw 0x0, time 2753415, (294,902), root:(1258,924),
state 0x0, button 6, same_screen YES
ButtonRelease event, serial 34, synthetic NO, window 0x3400001,
root 0x1c1, subw 0x0, time 2753415, (294,902), root:(1258,924),
state 0x0, button 6, same_screen YES
This is causing all kinds of problems as different applications interpret the events as real events and initiate their specified callbacks.
This happens under both the i3wm and the Cinnamon desktop and with different computer mice. This was not a problem before the update.