The flaw was publicised Wednesday on a security mailing list, along with a link to a fix for the problem . Updated versions of the affected software programs, which include the Mozilla, Firefox and Thunderbird browsers, have been released.
Developers said the flaw affected only Windows users, not computers running either the Macintosh or Linux operating systems.
The news comes as Microsoft has been dealing with a string of security flaws found in its Internet Explorer browser during the past several weeks. Some researchers had begun recommending that people worried about online security stop using the IE browser altogether.
Microsoft recommends that Web surfers using Internet Explorer keep abreast of the latest security warnings, and go to the company's Protect Your PC site.
Mozilla developers said that future versions of the Firefox Web browser would have automatic update notifications that would make it easier to notify users about security fixes.
