Apple has released 10.7.4 update to OS X Lion that improves the stability, compatibility and security of OS X. This update includes the security fix to the recent password hole for File Vault users. OS X 10.7.4 update includes Safari 5.1.6. Separately, Apple has also released an update to Safari 5.1.7.
To update, select from Apple menu->Software Update. You will be prompted to download and update OS X 10.7.4. Once OS X update is completed and your Mac is rebooted, visit Software Update again to update Safari to the latest v5.1.7.