Mozilla Firefox 18.0.2 is now available to download for Windows, Mac and Linux. The automatic update will be rolled out soon but if you can't wait then download Firefox from this link:
Firefox 18.0.2 for Windows (19.4 MB)
Right now, there is nothing in the Release Notes but word on the web says that Firefox 18.0.2 is a bug-fix version that accounted for almost 18% of all the crashes of the 18.0.1 version. You can read about the bug on Bugzilla.