Novel way of "spamming" via Calendar

A client tells me that on his iPhone and his PC notices with links appear all the time.
Made him clear cookies, etc. in iPhone and in his PC. Kept appearing, and he sends me a photo of one of the notices. It was from Calendar.
And I realized the ingenuity of the spammers. No coding required. Just craft a Calendar event, make it repeating, save it and send it by mail.
Both Apple Mail and Gmail have preferences to add events automatically to the Calendar.


This isn’t new. I saw this happen a few years ago but after a month or 2 of this crap hadn’t seen it again. Unfortunately if people are doing it again.