Description
WordPress Plugin WP Maintenance Mode & Site Under Construction is prone to a cross-site request forgery vulnerability. Exploiting this issue may allow a remote attacker to perform certain administrative actions and gain unauthorized access to the affected application; other attacks are also possible. WordPress Plugin WP Maintenance Mode & Site Under Construction version 1.8.2 is vulnerable; prior versions may also be affected.
Remediation
Edit the source code to ensure that CSRF protection is implemented with Nonce-like mechanism or disable the plugin until a fix is available
References
https://ithemes.com/wordpress-vulnerability-report-april-2021-part-4/
https://wordpress.org/plugins/wp-maintenance-mode-site-under-construction/#description