For further information on the issue in the extension powermail, please read the related advisory TYPO3-SA-2010-019 that was published today:
http://typo3.org/teams/security/security-bulletins/typo3-sa-2010-019/
TYPO3 13.4.10 and 12.4.29 maintenance releases published
The versions 13.4.10 and 12.4.29 of the TYPO3 Enterprise Content Management System have just been released.