Vulnerable are all versions of TYPO3 4.3.x. We will release TYPO3 4.3.3 and publish mitigation advices together with a security bulletin on
http://typo3.org on Friday, April 9 at 11:00 am CEST (9:00 am GMT).
Since this is a very important security fix, please be prepared to update your TYPO3 installations on Friday.
Until the advisory is out, please understand that we cannot provide any further information.
A Structured Content Initiative
Without extensions like Gridelements and Flux, creating and editing semantically and hierarchically structured content can be difficult in TYPO3.