"Selected state is not being conveyed to screen reader user
Selected state for the file type thumbnail button is not exposed to the screen reader"
The name, role, value, states, and properties of user interface components MUST be programmatically determinable by assistive technologies.
HOW TO FIX:
Fix this issue by using ONE of the following techniques:
1. Use the aria-selected attribute with the following four ARIA roles: gridcell, option, row, tab.
2. Use the aria-pressed attribute with a button (<button> element or custom role=""button"" element).
WAI-ARIA Recommendation: https://www.w3.org/TR/wai-aria-1.1/#aria-selected
WAI ARIA Authoring Practices: https://www.w3.org/TR/wai-aria-practices-1.1/#tabpanel
WAI-ARIA Recommendation: https://www.w3.org/TR/wai-aria-1.1/#aria-pressed
WAI ARIA Authoring Practices: https://www.w3.org/TR/wai-aria-practices-1.1/#button
States and properties are attributes used to convey essential information about an element to screen readers and other assistive technologies. Some roles require certain state and property information - such as the checked/unchecked state of a checkbox. Native HTML elements provide those required states and properties, so nothing more needs to be done. If you create a custom version of a native HTML element or a custom control or widget that does not have a native HTML equivalent, you must add the relevant states and properties using ARIA."