Webmin accepts basic authentication without session cookies when an attacker provides the 'User-Agent: webmin' header, allowing bypass of additional MFA requirements. Fixed in 2.640.
Webmin before 2.641 contains a stored cross-site scripting vulnerability in the email template description field of the System and Server Status module that allows low-privileged authenticated attackers to execute arbitrary JavaScript in the browser context of administrators by injecting unsanitized input stored in save_tmpl.cgi and rendered unescaped in list_tmpls.cgi.