This update is meant to correct an error introduced by Yoast 7.0, in March 2018. Victims of this bug will have suffered negative changes in rankings since the Yoast March 6 update.
If your rankings have steadily dropped sometime after March 6, and you use the Yoast SEO Plugin, your site may be a victim of the Yoast SEO Plugin bug.
What Went Wrong with Yoast SEO Plugin?
The ranking bug introduced what Yoast calls, “Panda-like problems” when it updated to the 7.0 version. This change affected settings to the way image redirects are handled. Fortunately, this update did not affect all users.
Is your SEO ok?