Observation Details
Tooltip content must be accessible via keyboard focus and hover which it is. The content must then be dismissible without moving the mouse pointer (on hover) or keyboard focus which it is not.
Remediation Notes
Ensure, all content that can be displayed by hovering via mouse pointer or receiving keyboard focus, is dismissible without moving the mouse pointer or keyboard focus. This usually is done by allowing ESC key to close the shown tooltip.
For ideas to build accessible tooltips, refer to e.g. Heydon Pickering – Inclusive Components – Tooltip.