Mozilla has released a new version, 19.0.2, of the Firefox browser for Linux, Mac OS X, and Windows. This is a security driven release, which provides a fix for a vulnerability [MFSA 2013-29] in the HTML editor component. More information is available in the Release Notes.
Because of the security content of this release, I recommend that you update your systems as soon as you conveniently can. You can use the update mechanism built into the browser (Help / About Firefox /Check for Updates), or you can download a complete installation package.