Over the past few weeks—and particularly over the retail adventure widely referred to as "Black Friday"—many Apple device owners experienced a new form of unsolicited and unwanted messages: a swarm of calendar alerts for online "deals" from spammers. The messages took advantage of the default settings in Apple's iCloud calendar service, allowing senders to automatically push calendar alerts to Apple iOS and macOS users and bypass e-mail entirely.
Getting rid of these calendar "invites" is a problem in itself, as declining them sends a message back to the spammer—confirming that someone actually is monitoring the iCloud account they targeted and encouraging them to send more messages. Getting rid of the unwanted alerts requires a multi-step workaround. But blocking them entirely only requires a single change to iCloud settings.
To get rid of the invites without sending a response to the spammer, you'll need to do the following: