Apple - How to remove Calendar event without the sender's notification
I found this free workaround over on Superuser.
Basically, you disable networking, delete the event, then delete the notification from email:
- Turn off networking on your Mac
- Delete the event from iCal
- Wait for the notification to show up in your Outbox
- Delete email from Outbox
- Turn back on networking
Once networking is back on, the sync will remove the other events from iCloud and your phone.
Echoing Jaime Santa Cruz's comment below, you should definitely block the sender. You have already confirmed your email because it (probably) already sent a notification that you accepted; best to be safe and not sorry.
As to your second question, "...it is enough reason for me stopping using the insecure Apple's calendar?" it would generate too much opinion to go into.
That said, I personally use Office365 Exchange Online ($48 for the year), Outlook.com, OneDrive and Azure for my cloud services with my iMac, MacBook Pro, XServe and (soon) a refurbished Mac Pro. I don't know if that says anything...
I had a similar issue but with a repeating event sent in Chinese script. The event repeated every day indefinitely and there was no option to delete without sending a delete confirmation to the Sender.
A bit of digging revealed that this is likely an invite sent directly to the iCloud calendar.
To try to stop this I have set that calendar invite to "Email" (you need to do this on the web icloud calendar options Setting>Preferences>Advanced>Invitations>EmailTo). Hopefully, nothing will be inserted into my calendar now without me accepting.
To remove the offending event, I created a Spam calendar on iCloud Calendar on the Web, moved the event to the Spam Calendar (on my mac), then deleted the Spam calendar (again, on the Mac).
Everything now seems to be in order.