Although no security fixes for this version have been listed in the Security Advisories page, the default for Java plug-ins to "click to play" is a welcome change as is script-generated password fields.
To get the update now, select "Help" from the Firefox menu at the upper left of the browser window, then pick "About Firefox." Mac users need to select "About Firefox" from the Firefox menu.
Additional information about the fixes and known issue are available in my blog post, Mozilla Firefox Version 26.0 Released (http://securitygarden.blogspot.com/2013/12/mozilla-firefox-version-260-released.html).
Update: The security updates have now been posted. Version 26.0 includes five (5) critical, three (3) high, three (3) moderate, and three (3) low security updates.
Security Advisories for Firefox (https://www.mozilla.org/security/known-vulnerabilities/firefox.html)