Since the last security update I installed, my iMac's power settings (for turning the screen off) have been reversed.
They're still set correctly in System Preferences: turn screen off after 3 minutes. However, since the update, the screen now turns *on* after 3 minutes.
Normally, I switch the screen off by moving the mouse to the corner of the screen, but I'm now finding the screen comes on *exactly* 3 minutes after doing this! I've tried rebooting, and changing the settings before changing them back, but it still does the same thing.