Provide references for CVE-2021-38339.
Where can I find more information about CVE-2021-38339?
References are available at: https://www.wordfence.com/vulnerability-advisories/#CVE-2021-38339, https://plugins.trac.wordpress.org/browser/simple-matted-thumbnails/tags/1.01/simple-matted-thumbnail.php#L122.