The Mozilla Foundation has urged users of its open-source Mozilla Application Suite, Firefox browser and Thunderbird e-mail client to download a small patch to work around a security vulnerability discovered this week.

The patches download a configuration change which disables the use of the :shell external protocol handler for running external programs by clicking on a hyperlink.

The security handling of this command may enable attackers to run arbitrary programs on Windows systems, although there are no problems for Mozilla users running other operating systems such as MacOS, Linux and other Unix variants, Mozilla said in a statement on its Web site.

The vulnerability affects Mozilla (version 1.7.0 and earlier), Firefox (0.9.1 and earlier), and Thunderbird (0.7.1 and earlier)

Full new versions of the free products are also available from the site, Mozilla said.