theme_get_setting() to get form values - this uses configuration with overrides (as it has to since it is primarily used at runtime). But this means that if any theme setting is overridden using config overrides then they can end up stored in configuration without the user intending that.
Steps to Reproduce
- Install standard
- Override a theme setting in settings.php for example $config['system.theme.global']['favicon']['use_default'] = FALSE;
- Go to /admin/appearance/settings - the override will change the form value - which it should not.
- Press save and the override will now be saved to the stored configuration - which it should not.
User interface changes
Data model changes