How to reproduce:
1. Create a new project
2. Open the Hierarchy (Window->General->Hierarchy)
3. Open the Scene view (Window->General->Hierarchy)
4. Left-click and drag the mouse in the Scene view at the top left spot and release the left mouse button at the same hight as a GameObject in the list of Hierarchy

Expected results: No GameObject gets highlighted in the Hierarchy
Actual results: A GameObject gets highlighted in the Hierarchy

Reproducible with: 2020.2.0b2, 2020.2.0b5
Not reproducible with: 2018.4.27f1, 2019.4.11f1, 2020.1.7f1, 2020.2.0b1

Notes:
- To reproduce this issue on the Game view you need to enter the Play Mode and before it loads move the mouse to the left side of the Game view
- Having the Hierarchy or Game view/Scene view docked or not doesn't matter