Since Moodle 4.0 navigation changes, the Quiz has a Back button, which exits the current attempt back to the quiz front page. This is all fine during a Quiz, which can be completed in bits, but pressing the button can have bad consequences for a student attempting a high-stakes quiz in a secure layout (such as a Safe Exam Browser enabled Quiz).

For example, when using the MacOS version of Safe Exam Browser, the "Leave site?" pop-up fails to appear, and instead, the quiz closes, and changes to a draft essay answer since the last autosave are lost.

I propose that the Back button should be removed from the secure quiz layout, and perhaps renamed in ordinary quizzes, to make it absolutely clear to the user, where they are going back to if they press it. 

See this forum discussion for extra context: https://moodle.org/mod/forum/discuss.php?d=448833