Please follow the below link in order to read the entire security bulletin covering all 11 extensions.
TYPO3-20080919-1: Collective Security Bulletin covering issues in 11 third party extensions:
In general the TYPO3 Security Team recommends you to read the following pages:
The TYPO3 Security Cookbook:
Make sure you are subscribed to the TYPO3 Announce List:
See all TYPO3 security bulletins: