Debian: CVE-2018-20681: mate-screensaver -- security update

mate-screensaver before 1.20.2 in MATE Desktop Environment allows physically proximate attackers to view screen content and possibly control applications. By unplugging and re-plugging or power-cycling external output devices (such as additionally attached graphical outputs via HDMI, VGA, DVI, etc.) the content of a screensaver-locked session can be revealed. In some scenarios, the attacker can execute applications, such as by clicking with a mouse.