Focus that enters any element must be able to leave that element. If the method requires more than ESC, Arrow Keys, or Tab, the user must be informed of the method.
When using the TAB key to navigate pages while testing for the 2.1.1 Keyboard criterion, take a note if the keyboard focus gets trapped on an element or in a loop that can't be escaped from.
It is required that if the method of leaving the keyboard trap requires the use of other keys aside from the Escape key, Arrow keys, or TAB/SHIFT + TAB, there must be an instruction that is visible and screen reader accessible indicating what is needed to leave the keyboard trap and return the user to where they were beforehand.
