Information
Hot Corners can be configured to disable the screen saver by moving the mouse cursor to a corner of the screen.
Rationale:
Setting a hot corner to disable the screen saver poses a potential security risk since an unauthorized person could use this to bypass the login screen and gain access to the system.
Solution
Perform the following to disable a Hot Corner set to Disable Screen Saver:
Graphical Method:
Open System Preferences
Select Desktop & Screen Saver
Select Screen Saver
Select Hot Corners... and turn off any corner that is set to Disable Screen Saver
Terminal Method:
Run the following command to turn off Disable Screen Saver for a Hot Corner:
$ sudo -u <username> defaults write com.apple.dock <corner that is set to '6'> -int 0
example:
$ sudo -u seconduser defaults write com.apple.dock wvous-tl-corner -int 0
$ sudo -u seconduser defaults read com.apple.dock wvous-tl-corner
0