The Modern Events Calendar Lite WordPress plugin before 5.22.3 does not properly sanitize or escape values set by users with access to adjust settings withing wp-admin.
The Modern Events Calendar Lite WordPress plugin before 5.22.2 does not escape some of its settings before outputting them in attributes, allowing high privilege users to perform Cross-Site Scripting attacks even when the unfiltered_html capability is disallowed.
Unvalidated input in the Modern Events Calendar Lite WordPress plugin, versions before 5.16.6, did not sanitise the mec[post_id] POST parameter in the mec_fes_form AJAX action when logged in as an author+, leading to an authenticated SQL Injection issue.