An addon using the UIDropDownMenu code taints, causing TargetUnit to fail when right-clicking on players in the social panels.
Steps to reproduce:
1) Rightclick the Blizzard Feedback icon. (Apparently, the Blizzard Feedback addon isn't secure).
2) Open who panel, in the social window
3) Type in the players name in the search field, and press enter
4) Right click on the players name in the search result, and select Target

10/20 13:06:13.656  Global variable UIDROPDOWNMENU_MENU_LEVEL tainted by Blizzard_FeedbackUI - Interface\FrameXML\UIDropDownMenu.lua:537 ToggleDropDownMenu()
10/20 13:06:13.656  Global variable UIDROPDOWNMENU_MENU_VALUE tainted by Blizzard_FeedbackUI - Interface\FrameXML\UIDropDownMenu.lua:538 ToggleDropDownMenu()
10/20 13:06:13.656  Global variable UIDROPDOWNMENU_OPEN_MENU tainted by Blizzard_FeedbackUI - Interface\FrameXML\UIDropDownMenu.lua:572 ToggleDropDownMenu()
10/20 13:06:13.656  Global variable UIDROPDOWNMENU_INIT_MENU tainted by Blizzard_FeedbackUI - Interface\FrameXML\UIDropDownMenu.lua:31 UIDropDownMenu_Initialize()
10/20 13:06:13.656  Execution tainted by Blizzard_FeedbackUI while reading UIDROPDOWNMENU_OPEN_MENU - Interface\FrameXML\UnitPopup.lua:787 UnitPopup_OnUpdate()
(... repeats of above line removed, since it's an OnUpdate ...)
10/20 13:06:22.328  Execution tainted by Blizzard_FeedbackUI while reading UIDROPDOWNMENU_OPEN_MENU - Interface\FrameXML\UIDropDownMenu.lua:26 UIDropDownMenu_Initialize()
10/20 13:06:23.937  An action was blocked because of taint from Blizzard_FeedbackUI - Interface\FrameXML\UnitPopup.lua:950 TargetUnit()


Any addon calling ToggleDropDownMenu, with level > 2, causes taint.
Steps to reproduce:
1) /run ToggleDropDownMenu(3)
2) start combat, without a target (as a spell caster, start casting a spell, and deselect target before spell has finished casting).
3) Select a target while in combat.

10/20 13:24:30.531  Global variable UIDROPDOWNMENU_MAXLEVELS tainted by MACRO_TAINT - Interface\FrameXML\UIDropDownMenu.lua:152 UIDropDownMenu_CreateFrames()
10/20 13:24:30.531  Global variable UIDROPDOWNMENU_MENU_LEVEL tainted by MACRO_TAINT - Interface\FrameXML\UIDropDownMenu.lua:537 ToggleDropDownMenu()
10/20 13:24:30.531  Global variable UIDROPDOWNMENU_MENU_VALUE tainted by MACRO_TAINT - Interface\FrameXML\UIDropDownMenu.lua:538 ToggleDropDownMenu()
10/20 13:24:30.531  Global variable _ERROR_COUNT tainted by MACRO_TAINT - Interface\FrameXML\BasicControls.xml:<Scripts>:16
10/20 13:24:34.625  Execution tainted by MACRO_TAINT while reading UIDROPDOWNMENU_MAXLEVELS - Interface\FrameXML\UIDropDownMenu.lua:725 CloseDropDownMenus()
10/20 13:24:35.562  Execution tainted by MACRO_TAINT while reading UIDROPDOWNMENU_MAXLEVELS - Interface\FrameXML\UIDropDownMenu.lua:725 CloseDropDownMenus()
10/20 13:24:35.562  Execution tainted by MACRO_TAINT while reading UIDROPDOWNMENU_MAXLEVELS - Interface\FrameXML\UIDropDownMenu.lua:725 CloseDropDownMenus()
10/20 13:24:40.484  Execution tainted by MACRO_TAINT while reading UIDROPDOWNMENU_MAXLEVELS - Interface\FrameXML\UIDropDownMenu.lua:725 CloseDropDownMenus()
10/20 13:24:40.500  An action was blocked in combat because of taint from MACRO_TAINT - Interface\FrameXML\TargetFrame.lua:61 TargetFrame:Show()
10/20 13:24:47.484  Execution tainted by MACRO_TAINT while reading TargetFrameDebuff1 - Interface\FrameXML\TargetFrame.lua:329 getglobal()
10/20 13:24:47.484  Execution tainted by MACRO_TAINT while reading TargetFrameDebuff1 - Interface\FrameXML\TargetFrame.lua:329 getglobal()
10/20 13:24:50.843  Execution tainted by MACRO_TAINT while reading UIDROPDOWNMENU_MAXLEVELS - Interface\FrameXML\UIDropDownMenu.lua:725 CloseDropDownMenus()
10/20 13:24:50.843  An action was blocked in combat because of taint from MACRO_TAINT - Interface\FrameXML\TargetFrame.lua:59 TargetFrame:Hide()