Updated: Comment #0
Problem/Motivation
in #1653026: Change notice: All configuration values are stored as strings we removed the automatic casting of all config scalar values to strings.
Proposed resolution
Explore using typed config in form validation and submission to ensure the values are cast to the correct type.
Remaining tasks
Write patch
User interface changes
N/a
API changes
Additional methods on \Drupal\Core\Form\ConfigFormBase