It seems that this flaw might affect up to hundreds of thousands of applications, exposing the user access tokens to advertisers and other parties. These tokens tend to be part of a spare set of keys which the Facebook apps will use in order to run selected actions on behalf of the user, including the posting of messages to a Facebook wall or sending RSVP replies to invitations.
The remedy is plain and simple – just close this potential security hole for good by changing your password, as that will automatically revoke all previously issued keys. Well, this news just gives you added incentive to change your passwords to a strong one regularly, no?