Can wp_insert_post_data filter be used to save custom field data?
You can access the raw $_POST data from the wp_insert_post_data filter, but there are probably better ways to intercept that data. save_post or similar hook would probably work As you are dealing with post_meta, update_post_meta uses update_metadata which provides the update_{$meta_type}_meta and updated_{$meta_type}_meta filters. Those may be the best for you but your question is … Read more