[Affected versions]:

• Firefox 65.0
• Firefox 66.0b3
• Nightly 67.0a1

[Affected platforms]:

• macOS 10.14
• macOs 10.13

[Prerequisite]:

• The Bookmarks Toolbar is active.

[Steps to reproduce]:

1. Launch the Firefox.
2. Right-click on the hamburger menu.
3. Hover the cursor over the Bookmarks Toolbar option and observe behaviour.
4. Take the cursor away and observe behaviour.

[Expected result]:

• The ckeck symbol changes to white when hovered and to black when the cursor it's taken away.

[Actual result]:

• On macOS 10.14:
  - the check symbol remains black while hovered most of the times;
  - when the check symbol is white while hover, it remains white when the cursor is taken away.
• On macOS 10.13: The check symbol dissappears sometimes when the cursor is taken away.

[Regression range]:

• I don't think this is a regression, but if there is one I will try to find it as soon as possible.

[Additional Notes]:

• Please look at the attached video.

Something odd is happening on mac here. Over to widget so they can have a look.