Mar 23, 2011 12:50 GMT  ·  By

While Firefox 4.0 undoubtedly captured the spotlight on March 22nd, 2011 hitting general availability, Mozilla made available for download two additional releases of its open source browser. Customers running older versions of Firefox can now update to Firefox 3.6.16 or Firefox 3.5.18, while they also have the option of upgrading to Firefox 4.0 Final.

Of course, it’s easy to guess what Mozilla would prefer end users to do. At the same time, the best course of action for customers not yet ready to make the jump to Firefox 4.0 is to deploy the latest updates offered to them.

“Firefox 3.6.16 and Firefox 3.5.18 are now available as free downloads for Windows, Mac, and Linux. As always, we recommend that users keep up to date with the latest stability and support versions of Firefox, and encourage all our users to upgrade to the very latest version, Firefox 4,” revealed Christian Legnitto, Firefox release manager.

In addition to the security updates included in Firefox 3.6.16 and Firefox 3.5.18, the two releases are also designed to increase protection of users leveraging HTTPS certificates.

Specifically, Mozilla has opted to blacklist some invalid HTTPS certificates. Firefox 4.0, 3.6, and 3.5 can now all identify several fraudulent SSL certificates and block them by default.

The open source browser vendor underlines that the invalid HTTPS certificates are not the result of Firefox issues.

“We strongly recommend that all Firefox users upgrade to these latest releases. If you already have Firefox, you will receive an automated update notification within 24 to 48 hours. This updates can also be applied manually by selecting “Check for Updates…” from the Help menu,” Legnitto added.

Since Firefox 4.0 is now out, my personal option is to move past Firefox 3.6 and Firefox 3.5 since the evolution introduced by the latest iteration is guaranteed to deliver a superior users experience to either of the two predecessors.

Firefox 3.6.x and Firefox 3.5.x for Windows are available for download here. Firefox 4.x Final for Windows is available for download here.

Firefox 4.x Final for Linux is available for download here.

Firefox 4.x Final for Mac is available for download here.