How to avoid this margin/border-issue on image captions?

This is what happens: - on a fresh Roots install.

What is the best way to fix it (the border/margin)?

In general, I’d like some margin around photos inserted via the Wordpress-editor. I’ve tested numerous ways of doing it, but what is considered to be ‘best practice’ ?

This issue was caused by the move to border-box sizing. There’s a fix on Github but the code it’s fixing isn’t the best and could do with a rework.

What is your suggestion on how to fix it?

I would carefully consider the thumbnail sizes and rewrite the code to make everything responsive. But if time is a factor, adding the extra 10px to the figure is fine and we haven’t been able to come up with anything more suitable (yet).

I see. And by adding 10px to the figure you mean putting a padding of 10 px on the figure?

No. I mean by editing lib/cleanup.php as per this commit.