Issue #2172561 by Gábor Hojtsy, alexpott: Config overrides may spill over to undesired places.

core/core.services.yml

core/includes/install.core.inc

core/includes/menu.inc

core/lib/Drupal/Core/Config/ConfigFactory.php

core/lib/Drupal/Core/Config/ConfigInstaller.php

...l/Core/EventSubscriber/ConfigGlobalOverrideSubscriber.php

core/lib/Drupal/Core/Form/ConfigFormBase.php

...config/lib/Drupal/config/Tests/ConfigLanguageOverride.php

...fig/lib/Drupal/config/Tests/ConfigModuleOverridesTest.php

...les/config/lib/Drupal/config/Tests/ConfigOverrideTest.php

...g/lib/Drupal/config/Tests/ConfigOverridesPriorityTest.php

...pal/config_translation/Form/ConfigTranslationFormBase.php

...e/ParamConverter/LocaleAdminPathConfigEntityConverter.php

...upal/migrate_drupal/Tests/d6/MigrateSystemConfigsTest.php

...les/search/lib/Drupal/search/SearchPageListController.php