Mozilla has released the second (there was no Firefox 3.6.1) update for Firefox 3.6.3 on April 1st. This update addressed the security vulnerability discovered and exploited last week during the Pwn2Own competition that challenges hackers to break the latest versions of the most popular web browsers.

Users should be prompted soon to update, but can obtain this update via Help the Menu and selecting Check For Updates… For complete list of changes and more information, please see the Firefox 3.6.3 Release Notes.

Source: Mozilla Links