I've noticed, that these sideboxes:
- subscribe to mailing
- recommend site
share same user object for data validation and processing.
I'm proposing to assign "special" to each of sideboxes so data don't get mixed, like <inp2:u.login .../> ; <inp2:u.subscriber .../> and <inp2:u.recommend .../>.
Now error will be raised, that there is no ID in request for mentioned above Specials. Now we need to change UsersEventHandler::getPassedID method to return current user's id for these specials.