Google is working on a solution to stop spammers from abusing a Google Calendar feature that automatically adds event invitations to its users’ calendars. Users have been reporting that some of these spam events have redirected them using malicious URLs to phishing landing pages looking to harvest their credentials and even malicious sites designed to spread malware. Users are advised not to reply to event invites from their smartphones but, instead, to follow the procedure detailed below and report all the events considered being spam. Google Calendar is also actively asking Twitter users who post about events added to their calendars without permission to report spam activity.
Source: https://www.bleepingcomputer.com/news/security/google-calendar-spam-got-you-down-a-fix-is-on-the-way/