gnome-screensaver 2.14.3, 2.22.2, 2.27.x, 2.28.0, and 2.28.3, when the X configuration enables the extend screen option, allows physically proximate attackers to bypass screen locking, access an unattended workstation, and view half of the GNOME desktop by attaching an external monitor.
http://git.gnome.org/browse/gnome-screensaver/commit/?id=2f597ea9f1f363277fd4dfc109fa41bbc6225aca
https://bugzilla.gnome.org/show_bug.cgi?id=593616
https://bugzilla.redhat.com/show_bug.cgi?id=557525
http://security-tracker.debian.org/tracker/CVE-2010-0285
https://exchange.xforce.ibmcloud.com/vulnerabilities/56366
http://www.mandriva.com/security/advisories?name=MDVSA-2011:093