I had an EKG done like a month ago for this reason. Turns out irregular heartbeats are a very normal thing in the amount I was experiencing them. In addition, I spent a lot of time indoors, sitting or lying on a couch, stressing about my health and the world, thus overreacting to normal changes in heart rhythm due to the sympathetic and parasympathetic system handing off to each other.

I've been fully vaccinated since August.

edit: Spelling, wording

Compromised versions are

coa: 2.0.3, 2.0.4, 2.1.1, 2.1.3, 3.0.1, 3.1.3

rc: 1.2.9, 1.3.9, 2.3.9

This exploit works by imitating a website which has camera/microphone priviliges, correct?

So could you prevent it by revoking all of said priviliges for all websites in Safari's settings?

On a vulnerable version you could do that. For clarity, the bugs that led to this have been fixed in the latest Safari version on all platforms.