Whenever we perform a search on a combo box menu (e.g. on the Search users combo box or the group selector (if groups mode is enabled) on the Assignment submissions page), the results come out in a list box as the user types on the text input part of the combo box. However, screen reader users have no idea about the search results because nothing is being announced about them.

We need to inform screen reader users of the search outcome. Adding something like "There are x items found" or "There are no items found" will be sufficient.