On Dec 21, 2012, Google twitted the confirmation of new Google Panda Update 23. Affecting the English Language Queries for around 1.3%. However, the last panda update was not announced officially but confirmed around 0.8% impact over English Language Queries.
There were rumours going all around about this update to be rolled out a couple of weeks ago, but Google denied of any of the updates. But this time, when no one could expect the same, right before holidays, Google has confirmed the refresh by itself on twitter.
The affected ones need not worry when a common rule is still applicable for an all-time success, whatever the update is.