Yellow or orange box around content
Chrome OS has an accessibility feature called “Spoken Feedback” that will read on-screen text. The element that is being spoken gets an orange outline around as seen in the screenshot below.
This feature can be toggled with Ctrl-Alt-Z, and it’s very easy to accidentally enable it when trying to interrupt a kiosk login with Ctrl-Alt-S.
If it does become enabled, use Ctrl-Alt-Z to disable it. You shouldn’t need to log in to turn it off. You can also disable it by logging in, going to settings, and searching for “Spoken Feedback”.