About a week ago, Mozilla released version 12.0 of the Thunderbird E-mail client. Thunderbird has now been updated to version 12.0.1, which fixes three bugs (none appears to be a security risk); further details are in the Release Notes. You can get the new version using the built-in update mechanism (Help / About Thunderbird / Check for Updates), or you can download an installation package here for all platforms: Windows, Mac OS X, and Linux.
Google has released a new version, 18·0·1025·168, of its Chrome browser, for all platforms: Windows, Linux, Mac OS X, and Chrome Frame. This new version fixes five identified security flaws, three of which Google rates as High severity. Further information on these changes is in the release announcement.
Windows and Mac users should get the new version via the built-in update mechanism. Linux users should get the updated package from their distributions’ repositories, using their standard package maintenance tools. You can verify that your system has been updated by clicking on the tools menu (the little wrench), and then on “About Google Chrome”.