is this example of mass assignment and should we throws exception for this?

Question

I have read the following article on Mass assignment https://cheatsheetseries.owasp.org/cheatsheets/Mass_Assignment_Cheat_Sheet.html

but still have some unknown, e.g.

public class User {
   private String userid;
   private String password;
   private String email;
   //private boolean isAdmin;  // NO this property (isAdmin) in User class

   //Getters & Setters
}

Here is the controller handling the request:

@RequestMapping(value = "/addUser", method = RequestMethod.POST)
public String submit(User user) {
   userService.add(user);
   return "successPage";
}

here is the request with more parameter than class User has (isAdmin=true)

POST /addUser
...
userid=bobbytables&password=hashedpass&[email protected]&isAdmin=true

As the class User has NO isAdmin property,

1. is the class User still has Mass Assignment security problem for this request?
2. should we throws exception if request parameter is more than the expected binding input parameter class?
3. related to question 2, if we ignore the extra parameter and returns response 200 (ok), is this right? As in a security check, our program is complained by return 200 for similar case.

As I see the article, the solution has NOT said to throws error or exception for this case.