Capabilities/mod/quiz:attempt

• This allows a user to attempt quizzes

Note that guest users can never attempt quizzes, even if you give guests the mod/quiz:attempt capability. This is because all information about a user's progress through the quiz must be stored in the database associated with the user doing the attempt, and each user can only have one attempt open at a time. Since all guest users in Moodle share a single user account, letting guests attempt quizzes would just cause a big mess where different guest users' actions would conflict with each other. Therefore, people logged in as guest are never allowed to attempt quizzes.