see https://github.com/tinymce/tinymce/blob/master/changelog.txt

it is probably better to do it soon so that we can test it in master in case we need to backport it to 2.4.x...

Version 3.5.8 (2012-11-20)
Fixed bug where html5 data attributes where stripped from contents.
Fixed bug where toolbar was annouced multiple times with JAWS on Firefox.
Fixed bug where the editor view whouldn't scroll to BR elements when using shift+enter or br enter mode.
Fixed bug where a JS error would be thrown when trying to paste table rows then the rows clipboard was empty.
Fixed bug with auto detection logic for youtube urls in the media plugin.
Fixed bug where the formatter would throw errors if you used the jQuery version of TinyMCE and the latest jQuery.
Fixed bug where the latest WebKit versions would produce span elements when deleting text between blocks.
Fixed bug where the autolink plugin would produce DOM exceptions when pressing shift+enter inside a block element.
Fixed bug where toggling of blockquotes when using br enter mode would produce an exception.
Fixed bug where focusing out of the body of the editor wouldn't properly add an undo level.
Fixed issue with warning message being displayed on IE 9+ about the meta header fix for IE 8.