To reproduce:

1. In a new project, create 3 prefabs
2. Drag one of them from Project View into Hierarchy
3. Observe the Project View

Expected: after dragging assets from Project View into other views, no blue lines (indicating where to put asset) and selection highlights should be visible in the Project View
Actual: line, indicating where will the asset be put or highlight, which indicates in which folder the asset will be put, are shown even though the dragged asset was put in other view

Reproduced in 2017.1.0b1, 2017.1.0b2, 2017.1.0b3
Did not reproduce in 5.6.0p4, 2017.1.0b4
Regression introduced in 2017.1.0b1