On September 5, Google updated its Search Quality Rater Guidelines. This update was brought to the attention of the SEO community from SEM consultant Mari Haynes in a tweet. This version places more emphasis on vetting news sources as well as YMYL content and its creators. It expands the basis for which a rater might apply the lowest ratings to content that may potentially spread hate.
The previous update occurred on May 16.
In a Search Engine Land post by George Nguyen, he shows us an analysis of the changes.