Easy Appointments <= 3.11.18 - Authenticated (Contributor+) Stored Cross-Site Scripting

The Easy Appointments plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the plugin's 'ea_full_calendar' shortcode in all versions up to, and including, 3.11.18 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.