Just yesterday, the most recent APEX patch set has been released. It is Release 4.2.2.00.11. The full version just as well as the patch set to apply to a 4.2.0 or 4.2.1 instance can be downloaded from here.
The full details can be found on Joel's Blog.
Nevertheless I will have a good look at the release notes, because they contain quite some important notes, which you should be aware of before upgrading. Especially, there were some changes made to the templates. So it is wise to upgrade your existing 4.2.0 / 4.2.1 instance with the patch set directly. If you export/import a 4.2.1 APEX application into a 4.2.2 instance, you cannot leverage the changes immediately, you would have to install the new theme and switch it then.
I will try to look at these issues in more detail ...