The Otter Blocks WordPress plugin before 3.2.8 does not properly sanitize and escape user-supplied block styling values before writing them into an inline stylesheet, allowing users with contributor-level access and above to inject arbitrary web scripts that execute when any visitor, including administrators, views the affected post.
https://wpscan.com/vulnerability/a2a19770-9ee2-4164-9ea6-a882cf0085e9/