Mozilla has pushed Firefox 27 to end users.
New features of Firefox 27 include running more than one service at a time with Firefox SocialAPI, allowing users to receive notifications, chat and more from multiple integrated services.
Other new features of Firefox 27 include:
Enabled TLS 1.1 (RFC 4346) and TLS 1.2 (RFC 5246) by default
Added support for SPDY 3.1 protocol
More details at http://www.mozilla.org/en-US/firefox/27.0/releasenotes/
Firefox 276 is available from http://www.mozilla.org/en-US/firefox/all/
UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_8_5) AppleWebKit/537.73.11 (KHTML, like Gecko) Version/6.1.1 Safari/537.73.11