HookScript will now function like SetScript if there is no script currently on the object.
Both Dropdown menus and the Vehicle Action Bar have been made less susceptible to taint.
Lua closures can now be directly assigned to frame scripts from XML using the following new format: <OnClick function="FunctionName"/>. The old format will continue to be supported indefinitely.
Several functions no longer accept unit tokens as parameters, and should now be used in conjunction with UnitName("token") instead. These functions include: AddFriend, RemoveFriend, SetFriendNotes, AddMute, DelMute, AddIgnore, DelIgnore, InviteUnit, UninviteUnit, GuildInvite, GuildUninvite, GuildPromote, GuildDemote, GuildSetLeaderByName, CalenderEventInvite
The secure handlers system was restricted with respect to OnUpdate/Timer handling and the ability to react to frame visibility. There is a new SetupAnimation method that addresses some of the restrictions. This change unfortunately removed some otherwise useful functionality around auto-hiding frames (and animation) but hopefully a future patch will address this.
NEW - SetUpAnimation(frame, updateFunc, posBody, totalTime, postFunc, reverse) - Sets the current 'animation' function for the frame (Available update functions are Show, Hide, SetPoint, SetScale, SetHeight, SetWidth, SetAlpha)