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[Daniel <daniel@xxxxxxxxx>]

I have discovered a side effect to this bug that implies a security
vulnerability.

You are in graphical tty7 and select the "switch user" option.
The xserver gets stuck trying to open a new graphical tty. You have black screen on tty8. You cannot go back to tty7.

Still you can open a non-graphical tty (tty1-tty6).
You have to login on the new tty, so you write username and password.

But all keyboard activity is still being captured on original tty7!!
You are exposing your login and password credentials (at least) to the foreground application on tty7.

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https://bugs.launchpad.net/bugs/1247189

Title:
  Ubuntu freezes completely when switching user

Status in “linux” package in Ubuntu:
  Confirmed
Status in “xserver-xorg-video-intel” package in Ubuntu:
  Confirmed

Bug description:
  I'm using a freshly installed Ubuntu 13.10. As soon as I click on a
  different user I want to switch to in the gearbox menu I get a black
  screen and nothing else is happening. I'm still able to SSH to that
  box and top does not show any process taking 100% CPU. Alt+sysrq+b is
  able to reboot the system. I had no problem like this with Ubuntu
  13.04 on the same computer.

  WORKAROUND: Disable the nvidia card in the BIOS.

  ProblemType: Bug
  DistroRelease: Ubuntu 13.10
  Package: lightdm 1.8.2-0ubuntu1
  ProcVersionSignature: Ubuntu 3.11.0-12.19-generic 3.11.3
  Uname: Linux 3.11.0-12-generic x86_64
  NonfreeKernelModules: wl
  ApportVersion: 2.12.5-0ubuntu2.1
  Architecture: amd64
  Date: Fri Nov  1 17:40:41 2013
  InstallationDate: Installed on 2013-10-30 (2 days ago)
  InstallationMedia: Ubuntu 13.10 "Saucy Salamander" - Release amd64 (20131016.1)
  MarkForUpload: True
  SourcePackage: lightdm
  UpgradeStatus: No upgrade log present (probably fresh install)
  --- 
  ApportVersion: 2.12.7-0ubuntu3
  Architecture: amd64
  AudioDevicesInUse:
   USER        PID ACCESS COMMAND
   /dev/snd/controlC0:  ubuntu     2816 F.... pulseaudio
  CasperVersion: 1.336ubuntu1
  CurrentDesktop: Unity
  DistroRelease: Ubuntu 14.04
  IwConfig:
   eth0      no wireless extensions.
   
   lo        no wireless extensions.
  LiveMediaBuild: Ubuntu 14.04 LTS "Trusty Tahr" - Alpha amd64 (20140105)
  MachineType: Acer Aspire 5755G
  MarkForUpload: True
  Package: linux (not installed)
  ProcFB:
   0 inteldrmfb
   1 nouveaufb
  ProcKernelCmdLine: file=/cdrom/preseed/username.seed boot=casper cdrom-detect/try-usb=true noprompt floppy.allowed_drive_mask=0 ignore_uuid initrd=/casper/initrd.lz quiet splash --
  ProcVersionSignature: Ubuntu 3.12.0-7.15-generic 3.12.4
  RelatedPackageVersions:
   linux-restricted-modules-3.12.0-7-generic N/A
   linux-backports-modules-3.12.0-7-generic  N/A
   linux-firmware                            1.119
  Tags:  trusty
  Uname: Linux 3.12.0-7-generic x86_64
  UpgradeStatus: No upgrade log present (probably fresh install)
  UserGroups: adm cdrom dip lpadmin plugdev sambashare sudo
  dmi.bios.date: 08/09/2012
  dmi.bios.vendor: Acer
  dmi.bios.version: V1.21
  dmi.board.asset.tag: Base Board Asset Tag
  dmi.board.name: JV51_HR
  dmi.board.vendor: Acer
  dmi.board.version: Base Board Version
  dmi.chassis.type: 10
  dmi.chassis.vendor: Acer
  dmi.chassis.version: V1.21
  dmi.modalias: dmi:bvnAcer:bvrV1.21:bd08/09/2012:svnAcer:pnAspire5755G:pvrV1.21:rvnAcer:rnJV51_HR:rvrBaseBoardVersion:cvnAcer:ct10:cvrV1.21:
  dmi.product.name: Aspire 5755G
  dmi.product.version: V1.21
  dmi.sys.vendor: Acer

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