Kimai is an open-source time tracking application. Prior to 2.58.0, POST /api/teams/{id}/members/{userId} and POST /api/teams/{id}/activities/{activityId} verify that a teamlead may edit the Team but do not verify access_user for the referenced User or view access for the referenced Activity. A teamlead can add users or activities outside the teamlead's manageable scope to an editable team, bypassing the narrower choices enforced by TeamEditForm and UserRepository::getQueryBuilderForFormType(). The resulting relationships can be trusted by RolePermissionManager::checkTeamAccessActivity() and other team-based authorization, visibility, reporting, and workflow logic. This issue is fixed in version 2.58.0.

Affected: Packagist: kimai/kimai

### Summary

Kimai contains an authenticated improper authorization vulnerability in Team-related assignment APIs. A Teamlead who can edit their own team can use backend API endpoints to add users or activities that fall outside their intended visible or manageable scope, even when the frontend correctly hides those targets.

This affects both team member assignment and team activity assignment. The issue is caused by treating "may edit this team" as equivalent to "may attach any referenced object to this team", without performing a second authorization check on the target user or activity.

### Details

The issue affects at least the following API routes:

- `POST /api/teams/{id}/members/{userId}` - `POST /api/teams/{id}/activities/{activityId}`

In both cases, the backend checks whether the caller may edit the `Team`, but it does not verify whether the referenced `User` or `Activity` falls inside the caller's allowed management scope.

For team member assignment, the frontend form correctly limits the visible user choices. In `src/Form/TeamEditForm.php`, the team edit form uses `UserType`:

```php $builder->add('users', UserType::class, [ 'label' => 'add_user.label', 'help' => 'team.add_user.help', 'mapped' => false, 'multiple' => false, 'expanded' => false, 'required' => false, 'ignore_users' => $team !== null ? $team->getUsers() : [] ]); ```

In `src/Form/Type/UserType.php`, the user selector is built from `UserRepository::getQueryBuilderForFo…