After you install this update 4484343, third-party add-ins or applications may crash when you process attachments through drag-and-drop or the clipboard.
This issue occurs when Outlook sets data in a publicly documented clipboard format (FileDescriptor) and the .NET Framework-based application does not correctly marshal the clipboard data. Applications may not have seen this issue earlier because Outlook previously set the FILEDESCRIPTOR.dwFlags field to 0. Outlook may now set some combination of the FD_CREATETIME, FD_ACCESSTIME and FD_WRITESTIME flags in the FILEDESCRIPTOR.dwFlags field, and provide valid FILETIME data in the ftCreationTime, ftLastAccessTime, and ftLastWriteTime members of the FILEDESCRIPTOR structure. To mitigate the issue, developers can update their code to read the count of FILEDESCRIPTOR structures from a pointer to the FILEGROUPDESCRIPTOR structure by using the Marshal.ReadInt32 method, or update the FILEGROUPDESCRIPTOR definition so that the Marshal.PtrToStructure method can successfully marshal the contents of the FILEGROUPDESCRIPTOR structure. See change in Outlook (April 2020 "2004") update for more information.
Third-party information disclaimer
Microsoft provides third-party information to help you find technical support. This information may change without notice. Microsoft does not guarantee the accuracy of this third-party contact information.