There's a plugin that adds a bunch of user profile fields and also dynamically changes fields visibility depending on current layout (i.e. makes certain fields hidden on registration layout). After a recent upgrade the dynamically set "hidden" attribute stopped working the way it did.

Steps to reproduce the issue

• Enable existing "profile" plugin,
• within onContentPrepareForm() function, apply "hidden" attribute to some field, e.g.

$form->setFieldAttribute('dob', 'type', 'hidden', 'profile');

in my case, it's conditional

if ($form->getName() == 'com_users.registration') {
    $form->setFieldAttribute('dob', 'type', 'hidden', 'profile');
}

Expected result

a field would become hidden (on registration if conditional)

Actual result

it is still visible in case the field is received through iteration:

foreach ($this->form->getFieldsets() as $fieldset) { // Iterate through the form fieldsets and display each one.
	$fields = $this->form->getFieldset($fieldset->name);
...
	foreach ($fields as $field) {// Iterate through the fields in the set and display them.			
		if ($field->hidden) {
			echo $field->input;
		} else echo $field->renderField();
	}
}

But it is hidden if I add an extra step:

foreach ($this->form->getFieldsets() as $fieldset) { // Iterate through the form fieldsets and display each one.
	$fields = $this->form->getFieldset($fieldset->name);
...
	foreach ($fields as $f) {// Iterate through the fields in the set and display them.			
		$field = $this->form->getField($f->fieldname, $f->group);
		if ($field->hidden) {
			echo $field->input;
		} else echo $field->renderField();
	}
}

System information (as much as possible)

PHP 5.6.28

Additional comments

I believe the bug was introduced with J3.6.5 update