[tabs_masterrace]

Got some too. What's super weird though, these calendar invites appear to have been sent from my iCloud email address to my gmail address, and also appear in the sent folder of my @me.com address: https://i.imgur.com/tz2TUh5.png

Anyone else can check in your gmail spam folder if you have those emails too and where they came from?

[plttn]

In that case, I'm going to hazard a guess that your iCloud email address was actually compromised, and is being used to send it to every address in your contacts.