Using a user with only READ permission I can change the due- and follow-up date in tasklist. An error message is displayed but the GUI changes nevertheless. After a refresh the dates are back to normal.
Steps to reproduce:
-have a task with or without due and follow-up date
-pick a user with read permission for that task
-if date is present press "X" or change date in date picker
-if no date is present only change date in date picker