For further information on the issue in extension "Frontend User Registration" (sr_feuser_register), please read the related advisory TYPO3-SA-2009-004:
http://typo3.org/teams/security/security-bulletins/typo3-sa-2009-004/
Regarding all other extensions listed above, please read the advisory TYPO3-SA-2009-005 (that represents a Collective Security Bulletin):
http://typo3.org/teams/security/security-bulletins/typo3-sa-2009-005/
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
See all TYPO3 security bulletins:
http://typo3.org/teams/security/security-bulletins/