Mozilla has released the 18th update for Firefox 3.6 on June 21st. This update fixed several security issues & stability issues. See release notes for full details. Users can get the update by going to Help >> Check For Updates.
Support for Gecko 1.9.2/Firefox 3.6 will continue. Next release will be Firefox 3.6.19, with a release date not yet announced. Firefox 3.5 has reached end of life support as of April 2011, depending on your operating system you should upgrade to Firefox 3.6 or 5.