Jens Askengren discovered that gnome-screensaver became confused when running under Compiz, and could lose keyboard lock focus. A local attacker could exploit this to bypass the user's locked screen saver.

=========================================================== 
Ubuntu Security Notice USN-537-1           October 23, 2007
gnome-screensaver vulnerability
CVE-2007-3920
==========================================================
A security issue affects the following Ubuntu releases:

Ubuntu 7.10

This advisory also applies to the corresponding versions of
Kubuntu, Edubuntu, and Xubuntu.

The problem can be corrected by upgrading your system to the
following package versions:

Ubuntu 7.10:
  gnome-screensaver               2.20.0-0ubuntu4.2

After a standard system upgrade you need to restart your session to affect
the necessary changes.

Details follow:

Jens Askengren discovered that gnome-screensaver became confused when
running under Compiz, and could lose keyboard lock focus.  A local
attacker could exploit this to bypass the user's locked screen saver.


Updated packages for Ubuntu 7.10:

  Source archives:

          Size/MD5:    22567 59f266ec6eb94b6a903e19b0ba0ddc0a
          Size/MD5:     1245 7a751fbd47821da72e6a980027a48011
          Size/MD5:  2320018 db71d89c66fa3a96b3b276403b5bb723

  amd64 architecture (Athlon64, Opteron, EM64T Xeon):

          Size/MD5:  1587250 2fdaaea4518774413cc48137d5f71f70

  i386 architecture (x86 compatible Intel/AMD):

          Size/MD5:  1570186 93d6f27e6334ae4022234d3fd165ade9

  powerpc architecture (Apple Macintosh G3/G4/G5):

          Size/MD5:  1605514 edeb052d5d0ccaa97085fd69f6b4f25a

  sparc architecture (Sun SPARC/UltraSPARC):

          Size/MD5:  1576650 9eaac4a063ae54792d052590c9bc4bc1