Affected versions

• 45.3.0esr, 67.0.b10, 66.0.3, 68.0a1 (2019-04-15)

Affected platforms

• Windows 10; Windows 7;

Steps to reproduce

1. Launch Firefox, DevTools inspector;
2. Open up the Rules inspector;
3. Click multiple times on the Hightlight square for any element;

Expected result

• element is selected;
• button/icon is highlighted;

Actual result

• the space next to the button is selected as well;
  (what makes sense is the whole row being selected, which happens not just the space alone)

Regression range

• not a regression;

Additional notes

• not reproducible on macOS 10.13 or Ubuntu 16.04;