The following are assumed to be assumption.
-Enable security must be checked on the screen of Manage Hudson.
-Select Hudson 's own user database with Security Realm.
-Allow users to sign up must be checked.
-Authorization : Anyone can do anything

Reproduction procedure:
1.Click Sign up in the upper right of the home screen.
2.Input the character string including any of the following characters to the Username text box.
For instance,｢?｣
/:*?"<>|(These are characters that cannot be used with Windows Explorer. )

3.Input an appropriate value to the text box of the remainder.
4.Sign up must click on a button.

Then, HTTP status 500 errors occur.
However, this user is added to People.
Moreover, the Delete link doesn't exist in the side menu on the user's page.