The The Events Calendar Shortcode & Block plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the plugin's `ecs-list-events` shortcode `message` attribute in all versions up to, and including, 3.1.2 due to insufficient input sanitization and output escaping on user supplied attributes. 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.