The The Events Calendar plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the Event Calendar Link Widget through the html_tag attribute in all versions up to, and including, 6.9.0 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with Contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.