Description of problem:

The Cinnamon lock screen does not lock all monitors. There are 3 monitors in this setup, on 2 graphics cards. The third monitor is not locked, only the first two are. Even clicking on windows on that monitor is possible. This is a serious security issue. See the attached screenshot.



Version-Release number of selected component (if applicable):

Fedora 23.



How reproducible:

Every time.



Steps to Reproduce:
1. Have a multi-monitor setup (possibly using a second graphics card).
2. In Cinnamon, lock your screen (Ctrl + Alt + L).
3. One monitor (probably the one on the second card) will not be locked, exposing whatever confidential information might be visible there to onlookers and even allowing them to click on buttons!



Actual results:

The lock screen does not lock the screen.



Expected results:

The lock screen should lock the screen. It's the only thing it's supposed to do.



Additional info:

I've already opened a Cinnamon bug:
https://github.com/linuxmint/Cinnamon/issues/5150
However, nobody has commented on this in a month. Since this is a major security flaw, I'm opening this bug against Fedora as well. This should be fixed as soon as possible. Not being able to lock the screen is unacceptable.