I spent +3 hours between Yahoo and Apple customer service. I recently noticed a new calendar named "sys-ext-events$ on all of my Apple devices. Not knowing what this is, I tried to delete but it kept coming back. I thought my devices were infected, putting my personal files at risk. Apple said it was a Yahoo issue and Yahoo said it was an Apple issue. Apple eventually directed me to calendar.yahoo.com where I was able to see my calendars. There is one listed as "Events from Mail." I tried to delete but cannot. It was confirmed by your representative that "sys-ext-events$" calendar on my devices was related to the "Events from Mail" calendar on the web version of my Yahoo account. Bottom line is I did not knowingly provide approval for Yahoo to add an oddly named calendar to my account. It caused much consternation as I believed I was hacked and my personal email communications were at risk. I am currently in a fraud protection program because of leaks and have been so for years. Yahoo needs to provide the ability to delete this unwanted calendar, and provide much better notification this type of addition will occur. You also need to train your customer service people better since none of them were aware of the sys-ext-event$ calendar. Very frustrating experience.