Stored XSS in the Contact Form 7 Datepicker plugin through 2.6.0 for WordPress allows authenticated attackers with minimal permissions to save arbitrary JavaScript to the plugin's settings via the unprotected wp_ajax_cf7dp_save_settings AJAX action and the ui_theme parameter. If an administrator creates or modifies a contact form, the JavaScript will be executed in their browser, which can then be used to create new administrative users or perform other actions using the administrator's session.

References

• https://nvd.nist.gov/vuln/detail/CVE-2020-11516
• https://www.wordfence.com/blog/2020/04/high-severity-vulnerability-leads-to-closure-of-plugin-with-over-100000-installations/