Thousands of Google users are exposing the contents of their calendars to the public. The problem is due to misconfiguring Google Calendar to share its contents with others. Using advanced search parameters (dorks) on Google can reveal meetings, interviews, events, internal information, presentation links, and locations for some companies. The information is indexed by search engines and can include email addresses as well as private events from individuals and businesses. Google says Calendars are private by default for G Suite and consumer users.
Source: https://www.bleepingcomputer.com/news/security/misconfigured-google-calendars-share-events-with-the-world/