Hi folks 
We’re introducing some changes to the way focus behaves in @atlaskit/button@^16.6.0.
Button previously had accessibility issues with its focus state. This problem was most severe with the primary, warning, selected and danger appearances where the focus color would blend with the underlying background color of the button. As part of ongoing visual uplift of the Atlassian Design System we’ve addressed this behavior.
The key aesthetic change to Button is the introduction of an offset border - where the focus ring is now visually separated from the Button. This was brought in to ensure we have the required 3:1 contrast between the focus border and the button background. Before this change, we were not meeting WCAG requirements.
Cheers!