Mozilla has released the latest and new version of Firefox browser with some fixes from the previous version. It had some serious security and vulnerability issues. Here are some updates done from the previous version -

• Fixed security issues like information stealing via local shortcut files, memory corruption leading to browser crash and several other issues related to the browser security.
• Fixed stability issues.
• Beta releases for the Bulgarian, Esperanto, Estonian, Latvian, Occitan, and Welsh languages.
• Enabled additional EV root certificates.
• In Firefox 3.0.2, some passwords that were saved by password manager did not work properly and did not automatically show up although saved. This error is fixed.
• In some cases, Firefox would not properly save proxy settings for protocols other than HTTP.
• Official releases for the Icelandic and Thai languages are now available.

There were hundreds of bugs reported by firefox users who used the previous version and so upgrading the browser is the best. You can check about the firefox update here.

Not sure what changes were made, or there was a new version for windows user, but this update for Mac is confirmed.