I am running VirtualBox 5.2.16 with the appropriate Extension-Pack and GuestAdditions, I have a number of VMs installed.
I noticed recently that in-spite of enabling Bidirectional Shared Clipboard and Drag'n'Drop on a Linux Centos 7.5, when dragging a file from the Linux (VM) Guest Desktop to the Windows Host Desktop, it works fine. But when dragging a file from Windows Host to the Linux Guest, I get the + sign and the process does not give an error but the file does not appear on the desktop.
I don'y know if this is a bug or I missed something out!. Nevertheless, this functionality works fine between Windows Host and Windows Client.
After some investigations, I found on the Linux guest a folder "/tmp/VirtualBox Dropped Files/" which has all the dragged files inside sub-folders with date stamp names. I opened the sub-folders and copied the files to the Linux desktop to use them. I then deleted the empty date stamp folders.
I thought I will share this with the community.
Simple07.