Install https://github.com/moodleou/moodle-quizaccess_safeexambrowser Create a new quiz. Type garbage into the new Allowed browser exam keys field. Try submitting the form, verify you get a validation error. Delete the allowed keys, but cause a validation error somewhere else. (E.g. enter a feedback boundary, but no feedback.) Make sure the validation still works. Fix the other validation problem, and enter a valid browser key (that is, any 64-bit hex string like 81aad4ab9dfd447cc479e6a4a7c9a544e2cafc7f3adeb68b2a21efad68eca4dc. Ensure you can save the form.