hmmm, apparently there was a 23.0.1, probably an important security fix for 23, that came about 2 weeks after version 23, but they are on a 6 week release cycle, and no minor versions come out after the next major version. You can see it in their release history: https://ftp.mozilla.org/pub/mozilla.org/firefox/releases/ There was a 19.0.1 and 19.0.2, but no more versions of 19 came out after 20 came out. 20 was the next version and got all the security fixes. 24 got all the security fixes for 23(.0.1). You can also see it in their release notes from today. They say to upgrade to 24 or 17.0.9 ESR. Those are the only versions getting security fixes. There won't be a 23.0.2.