Firefox is not the only one getting an update, there's a new Chrome in the stable channel as well. The latest Chrome 23.0.1271.91 is a stability and security update, Chrome 23 has been in the stable channel for about three weeks, meaning it's halfway through its cycle.
The big updates are the security fixes, Google lists all of the bugs, but their description won't be published until most people upgrade to the latest, secured version.
Other than the security issues, the latest Chrome fixes a problem with the Flash Player plugin – audio didn't work when the speakers were configured as Quadrophonic, a rather rare four-speaker setup.
The latest update also fixes an issue for Windows Server 2003 users, which can't be that many, Chrome crashed to the familiar "Aw, Snap" page in all instances. It was a rather serious problem for the few people that rely on Windows Server 2003.