The update also --in the past, opening GarageBand would change Safari's preferences to always accept cookies (as opposed to the default of accepting cookies only for the sites being visited), which could allow third parties and advertisers to track a user's Web activity. With this update installed, Safari's cookie preferences won't be changed (although if you've launched GarageBand previously, you'll need to check Safari and change the preference back if you so desire).
GarageBand 5.1 is available or via OS X's Software Update mechanism.