Fullscreen Virtualbox session still available without login when coming out of suspend

[123vier]

Virtualbox: Version 5.0.10_Ubuntu r104061
uname: Linux 4.2.0-25-generic #30-Ubuntu SMP Mon Jan 18 UTC 2016 x86_64 x86_64 GNU/Linux
Ubuntu 15.10

When returning from suspend by reopening the laptops lid, the fullscreen session of virtualbox can be resumed without ever seeing the login screen.

Only when closing/minimizing the virtualbox instance the login screen pops up.

ProblemType: Bug
DistroRelease: Ubuntu 15.10
Package: gnome-screensaver 3.6.1-7ubuntu1
ProcVersionSignature: Ubuntu 4.2.0-25.30-generic 4.2.6
Uname: Linux 4.2.0-25-generic x86_64
ApportVersion: 2.19.1-0ubuntu5
Architecture: amd64
CurrentDesktop: Unity
Date: Fri Jan 29 10:51:37 2016
EcryptfsInUse: Yes
GnomeSessionIdleInhibited: No
GnomeSessionInhibitors: None
GsettingsGnomeSession:
 org.gnome.desktop.session session-name 'ubuntu'
 org.gnome.desktop.session idle-delay uint32 300
InstallationDate: Installed on 2015-10-27 (93 days ago)
InstallationMedia: Ubuntu 15.10 "Wily Werewolf" - Release amd64 (20151021)
SourcePackage: gnome-screensaver
Symptom: security
Title: Screen not locked when coming out of suspend/hibernate
UpgradeStatus: No upgrade log present (probably fresh install)