For further information on the issue in extension "Virtual Civil Services" (civserv), please read the related advisory TYPO3-SA-2009-007:
http://typo3.org/teams/security/security-bulletins/typo3-sa-2009-007/
For further information on the issue in extension "Modern Guestbook / Commenting system" (ve_guestbook), please read the related advisory TYPO3-SA-2009-009:
http://typo3.org/teams/security/security-bulletins/typo3-sa-2009-009/
For further information on the issue in extension "CWT Community" (cwt_community), please read the related advisory TYPO3-SA-2009-006:
http://typo3.org/teams/security/security-bulletins/typo3-sa-2009-006/
Regarding all other extensions listed above, please read the advisory TYPO3-SA-2009-008 (that represents a Collective Security Bulletin):
http://typo3.org/teams/security/security-bulletins/typo3-sa-2009-008/
In general the TYPO3 Security Team recommends you to read the following pages:
The TYPO3 Security Cookbook:
http://typo3.org/fileadmin/security-team/typo3_security_cookbook_v-0.5.pdf
Make sure you are subscribed to the TYPO3 Announce List:
http://lists.netfielders.de/cgi-bin/mailman/listinfo/typo3-announce
See all TYPO3 security bulletins:
http://typo3.org/teams/security/security-bulletins/