The team is very close to releasing WordPress 3.5, but had to push it back another day with a sixth release candidate (they were very busy over the weekend) to fix how TinyMCE (the Visual editor tab) handles “ridiculous object and embed tags.” To sum it all up in one handy and concise Tweet, this:
WordPress 3.5 now runs a custom TinyMCE schema tailored to the HTML5 living standard. We audited the whole spec to keep your content intact.
— Daryl Koopersmith (@koop) December 10, 2012
So, if you’re a fan of using crazy embeds in your posts, particularly HTML5 bits, please test this RC. To test it, place your crazy embed in the Text editor tab, switch back to the Visual editor tab to make sure that it’s still there, switch back to the Text editor tab to make sure it isn’t mangled, then switch to back to the Visual editor tab to confirm it isn’t mangled there either. The team is looking for regressions, so please check in WordPress 3.4.2 as well.
If you’re a plugin or theme developer, this may very well be your last chance to check your products for incompatibilities before WordPress 3.5 is officially released, so don’t delay any longer!