10 critical vulnerabilities, 2 high vulnerabilities, 1 moderate, and 2 low.

You can read all the latest about what security components were vulnerable here: http://www.mozilla.org/security/announce/


You can install the latest update within Firefox... click Help > Check for updates, or Help > Apply downloaded update.

I downloaded the updated version, and my mozilla crashed afterwards. I had to rollback to version 3.5.30729 before it would work again. I am running Windows 7 ultimate, Any ideas??

Try to completely reinstall it.

I was wondering whether 3.6.13 needs to be upgrade?

No, currently 3.6.13 is still the latest unless you upgrade to beta 4.