If you have your Windows scaling set above 100%, there will be a small band of pixels shown in the search boxes used throughout the editor. You may need to resize the window containing the search box in order to see it.

1. Set your Window scaling above 100%
2. Open Unity
3. Create a new project with any settings
4. Undock the Hierarchy
5. Resize the Hierarchy window

Expected Result:
As the window is resized, the search box is displayed correctly.

Actual Result:
A small band of pixels is shown on the right hand side of the search box, where the clear button normally begins.

Tested on Windows.

Occurs on 2018.3.7, 2019.1.0b11, 2019.2.0a11