Mozilla Foundation announced the availability of Firefox 2.0 Beta 2, which includes many enhancements including a few that increase the browser's security. While Mozilla Foundation does not recommend that people use the newly released beta in production interested parties, including developers and experienced beta testers, can download the new version and take it for a test drive.
When you do you'll find that this release includes Phishing Protection, which is the most signifanct change in terms of security. The feature, turned on by default, uses an updateable list of known phishing sites. When you visit a site Firefox checks that site against the list. Take note that for this release the list is for testing purposes only and as such is limited in size. Other security improvements, not detailed by Mozilla, relate to changes in the add-ons manager and extension system.
The next version, Firefox 2.0 Release Candidate 1 (RC1), is currently scheduled to be released on September 19. The final released date, originally slated for October, has been postponed. Mozilla's Developer Calendar current doesn't specify the expected final release date.