The Norwegian developer rolled out the first release candidate for Opera 12.14. The reason behind this unexpected update (there was no beta stage for it) is trouble with the recently released Opera 12.13.
Less than a week after releasing Opera 12.13, the developer is urging users that work with the stable version to go back to the 12.12 build on account of major issues with crashes. They have already replaced the download link for the faulty version of the browser from the official page.
Opera 12.13 would crash when trying to update multiple extensions. This would happen when checking for a browser update (either manually or in the background), with several extensions requiring updating as well.
The release candidate for 12.14 fixes this issue along with a couple of others, such as failure on looking up CSS property or nested importScripts() usage breaks in Web Workers.
All this considered, we might see a stable Opera 12.14 emerging by the end of the week, if no showstoppers prevent it.
[Update, February 5, 2013, later]: Opera 12.14 took less than we expected to reach the stable stage. At the moment it is available for download (build 1738), albeit no official notes have been released and the official download page still offers version 12.12. The official release may undergo some changes, though.