SigiLee

I posted about this very same problem. It doesn’t seem to be that the phpbb user just has admin rights, but more like the user gets transformed into the admin user.
Take a look at the “Howdy” message in the WordPress top bar on the right side. When I first visit your WP page with my phpbb user, it says “Howdy my_phpuser”, on accessing the admin page, the message changes to “Howdy admin”.
Is this the same for you?

My topic: http://ww.wp.xz.cn/support/topic/plugin-wp-phpbb-bridge-phpbb-bridge-wth-any-user-has-access-to-wp-site-admin

Some response would be very welcomed since this seems to be very broken at the moment, or we are doing something very wrong. In either way it would be nice which is the case.