The gesture handling code in Clutter before 1.16.2 allows physically proximate attackers to bypass the lock screen via certain (1) mouse or (2) touch gestures.
https://euvd.enisa.europa.eu/vulnerability/EUVD-2015-3276
https://bugzilla.redhat.com/show_bug.cgi?id=1227098
https://bugzilla.gnome.org/show_bug.cgi?id=749847