The Add Sidebar WordPress plugin is vulnerable to Reflected Cross-Site Scripting via the add parameter in the ~/wp_sidebarMenu.php file which allows attackers to inject arbitrary web scripts, in versions up to and including 2.0.0.
https://www.wordfence.com/vulnerability-advisories/#CVE-2021-34666
https://plugins.trac.wordpress.org/browser/sidebar-adder/tags/2.0.1/wp_sidebarMenu.php#L124