• VSCode Version: 1.25.0-insider
• OS Version: Windows 10 Home - 1803

Steps to Reproduce:

1. Select the Explorer sidebar tab
2. Drag the Outline or File Hierarchy views as if to rearrange them
3. Move the cursor over an item in the Open Editors view
4. The individual editors will change color along with the entire view, making it seem as if you can drop a sidebar view into an open editor and something will happen. What should actually happen is that the view should highlight (since its location will be replaced; it does do this), but the individual items should not be affected.

Screenshot:

I am holding the File Hierarchy view over the index.js file in that screenshot.

Does this issue occur when all extensions are disabled?: Yes