The Calendar Event Multi View WordPress plugin before 1.4.07 does not have any authorisation and CSRF checks in place when creating an event, and is also lacking sanitisation as well as escaping in some of the event fields. This could allow unauthenticated attackers to create arbitrary events and put Cross-Site Scripting payloads in it.
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.
The web application does not, or cannot, sufficiently verify whether a request was intentionally provided by the user who sent the request, which could have originated from an unauthorized actor.