Virtualbox steals password from lock screen

[Philipp]

I just experienced some really troubling behavior from the Ubuntu lock screen:
I had been working in a VirtualBox virtual machine (running Windows 10, if that matters) and after being away from the computer for a while, Ubuntu locked the screen. When I entered my password and confirmed it with return, the lock screen went away and I was surprised to see my password in a terminal I had had open in the virtual machine.
When I tried to close the VirtualBox window, Ubuntu went back to the lock screen. I was not using full-screen mode in VirtualBox.

Here are the installed versions of the relevant packages:
virtualbox-5.0: 5.0.20-106931~Ubuntu~xenial
gnome-screensaver: 3.6.1-7ubuntu5
lightdm: 1.19.5-0ubuntu1

This happened on Ubuntu 16.10 with an x86_64 4.8.0-27-generic kernel.

[Marc Deslauriers (mdeslaur)]

What desktop environment are you running?

[Philipp (c-ubuntu-f)]

This happened with the default Unity desktop.

[Launchpad Janitor (janitor)]

[Expired for gnome-screensaver (Ubuntu) because there has been no activity for 60 days.]