If you add questions to a quiz using the ‘New Question Group’ function, then changes in the question bank will be reflected in the quiz.

Screenshot highlighting new question group button in Canvas

However, if you add a question using the ‘Find Questions’ function, this creates a copy of the question from the bank in its current form. Any changes to the question in the bank will NOT be reflected in the quiz from that point on.

Screenshot highlighting find questions button in Canvas

Canvas Guide: How do I create a quiz with a question group linked to a question bank?