Crash in CFileDialog with Feature Update to Windows 10 Version 1909 via Enablement Package (KB4517245)

[Marco Nef]

I'm writing because of problems our customers encounter. After installing KB4517245 on some installations our product crashes because of problems in CFileDialog (MFC). The crash happens when the customers click the search field on the top right corner. No input is needed just a click to set the focus in the search field.

At least on some machines the deinstallation of KB4517245 helped to solve the problem.

The callstack is as follow:

Call Stack:
00007ffb847b8660()
user32.dll!UserCallWinProcCheckWow()
user32.dll!DispatchClientMessage()
user32.dll!__fnINLPCREATESTRUCT()
ntdll.dll!KiUserCallbackDispatcherContinue()
win32u.dll!NtUserCreateWindowEx()
user32.dll!VerNtUserCreateWindowEx()
user32.dll!CreateWindowInternal()
user32.dll!CreateWindowExW() Unknown
Windows.UI.FileExplorer.dll!HostedApplicationBase::CreateHostWindow(struct tagRECT const &)
Windows.UI.FileExplorer.dll!HostedApplicationBase::InitializeAsync$_ResumeCoro$2()
Windows.UI.FileExplorer.dll!HostedApplicationBase::InitializeAsync$_InitCoro$1()
Windows.UI.FileExplorer.dll!HostedApplicationBase::InitializeAsync(struct HWND__ *,struct tagRECT const &,struct winrt::Windows::Internal::ApplicationHosting::ICoreApplicationBridgeFactory)
Windows.UI.FileExplorer.dll!CModernSearchBox::InitializeSearchUIAsync$_ResumeCoro$2()
Windows.UI.FileExplorer.dll!CModernSearchBox::InitializeSearchUIAsync$_InitCoro$1()
Windows.UI.FileExplorer.dll!CModernSearchBox::InitializeSearchUIAsync(void)
Windows.UI.FileExplorer.dll!CModernSearchBox::UIActivateIO(int,struct tagMSG *)
Windows.UI.FileExplorer.dll!CModernSearchBox::OnClick(struct tagPOINT) Unknown
Windows.UI.FileExplorer.dll!CModernSearchBox::WndProc(struct HWND__ *,unsigned int,unsigned __int64,__int64,bool &)
Windows.UI.FileExplorer.dll!CModernSearchBox::s_WndProc(struct HWND__ *,unsigned int,unsigned __int64,__int64)
user32.dll!UserCallWinProcCheckWow()
user32.dll!CallWindowProcW()
comctl32.dll!CallNextSubclassProc()
comctl32.dll!DefSubclassProc()
Windows.UI.FileExplorer.dll!AccessibleSubWndProc<CModernSearchBoxAcc>()
comctl32.dll!CallNextSubclassProc&#30;()
comctl32.dll!MasterSubclassProc()
user32.dll!UserCallWinProcCheckWow()
user32.dll!DispatchMessageWorker()
user32.dll!IsDialogMessageW()
user32.dll!DialogBox2()
user32.dll!InternalDialogBox()
user32.dll!DialogBoxIndirectParamAorW&#30;()
user32.dll!DialogBoxIndirectParamW&#30;()
comdlg32.dll!<lambda>(void)()
comdlg32.dll!CFileOpenSave::Show(struct HWND__ *)
mfc140u.dll!CFileDialog:oModal() Line 775 C++

The application was developped with Visual Studio Professional 2015, v14.0.25431.01 Update 3.

Because we can't reproduce this problem we're in urgent need for some advice what we could do to solve that problem programmatically. Thank you!

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