All users being able to complete tasks via REST

I have a task that has the assignee set to user1. But, all users in the system are being able to complete the task via REST. I also have authorization enabled and working. How can I make sure that only the assigned user is able to complete the task?

Hey, did you find any solution to this?

Dear @rajshreeee ,

Do you have any solution for this problem? Because I am also facing the same problem. Kindly share the detail if you have.

Thanks & Regards,
Prakash R.