Describe CVE-2021-4356.
What is CVE-2021-4356?
The Frontend File Manager plugin for WordPress is vulnerable to Unauthenticated Arbitrary File Download
 in versions up to, and including, 18.2. This is due to lacking authentication protections, capability checks, and sanitization, all on the wpfm_file_meta_update AJAX action. This makes it possible for unauthenticated attackers to download arbitrary files on the site, potentially leading to site takeover..