How to avoid Outlook's security warning on a .ics file

Question

I am creating a .ics file using iCal.Net. THe file is correct and works. But when I go to open it, I'm using Outlook on Windows, I get:

But I get invites all the time in Outlook that I accept without this warning. So I looked on meetup.com and what it has for adding to the calendar is:

So, do I need to create 4 different calendar files so users can then select the appropriate one? Or is there a way to create a .ics that all the calendar apps accept without a security warning?

Answer 1

Looks like it is an acknowledged bug by Microsoft

https://support.microsoft.com/en-gb/office/outlook-prompts-security-notice-opening-ics-files-after-installing-protections-for-microsoft-outlook-information-disclosure-vulnerability-released-dec-12-2023-df8647ef-1828-421b-a266-79120b6190bd