Regarding the famous "Additional security info required":
First, you press the "install" button in AppStore and you get the usual password prompt. This is AppStore asking your password, application did not launch yet.
Next, if password was correct, store will launch installer, application icon appears and "Additional security info required" popup. Looks like APP is asking for something. Press next, and it will PROMPT FOR PASSWORD (!! for the same password you just entered in AppStore dialog!!) again! If that is not a phishing attempt to get your password, what it is then?
Many posts here will refer to some article in "Mac Rumors" (!!?) saying that this is "increased" Apple security. None has posted link to actual Apple announcement of such "security enhancement". So, basically, some people running some website THINK that this must be legitimate from Apple.
Check your account in this forum, check it in Mac App Store, and most likely your account will work just fine, without asking any additional "security info"!
Now, if this is indeed legitimate from Apple (which I do not want to try, risking my personal info), this must be the dumbest "security enhancement" ever. Making Application you are installing to ask for your password and all kinds of info which may be used to compromise your account, is just plain crazy.
Probably, there are only two possibilities.
First, and most likely is that Apple's "security experts" are not really experts in the common understanding of this word.
Other possibility, somebody might be trying to create a new breed of Apple users - you tell them for security reason they must run naked three times around their house and they will do it, without ever questioning the request.