Mozilla has released a new version, 4.0.1, of its Firefox Web browser for Mac OS X, Linux, and Windows. The new version fixes some bugs that affected the browser’s stability; it also fixes two serious security vulnerabilities. More information about the changes is available in the Release Notes.
Because of the security fixes in this release, I recommend that you update as soon as you conveniently can. You can get the new version via the built-in update mechanism (Help -> About Mozilla Firefox -> Check for Updates), or you can download an installation package here.
For those users who are still running Firefox 3.6.x, Mozilla has also released a new version 3.6.17 with security and stability updates, which is available here. Since Mozilla intends to discontinue support for the 3.6.x browsers later this year, I do encourage you to update to version 4 as soon as you can.