The company is using new algorithms to boost authentic posts in your news feed, while demoting posts that are likely to be fake or sensational news, according to a Facebook blog post:
With this update, we’re adding new universal signals to determine whether a post might be authentic. To do this, we categorized Pages to identify whether or not they were posting spam or trying to game feed by doing things like asking for likes, comments, or shares. We then used posts from these Pages to train a model that continuously identifies whether posts from other Pages are likely to be authentic. For example, if Page posts are often being hidden by people reading them, that’s a signal that it might not be authentic.