Steps to Reproduce

    <groupbox mold="3d">
        <caption iconSclass="z-icon-angle-down">
            title
        </caption>

        <textbox/>
    </groupbox>

1. press the tab key to focus on the caption of the groupbox
2. check document.activeElement, it's span#zK6P2-toggle.sr-only.sr-only-focusable

Current Result

but no visual effect on the groupbox, so end-users don't know where the focus is

Expected Result

there is a visible, visual effect on the caption

Debug Information

• the CSS class name sr-only, sr-only-focusable don't follow zk convention, starting with z-

Workaround

.z-caption:focus-within