This has been an issue for a couple of weeks now.
The background of the tag filter widget bleeds out beyond it's bounding border.
The background is on .oo-ui-tagMultiselectWidget.oo-ui-widget-enabled.oo-ui-tagMultiselectWidget-outlined
But the border is on the child: .mw-rcfilters-ui-filterTagMultiselectWidget.oo-ui-widget-enabled .oo-ui-tagMultiselectWidget-handle
this element also has a top margin, and that combination is the cause.
Safari.