If you unfollow someone on Twitter right now, Twitter might send them a notification. Thanks to the bug, which has been active for over a week now, user X might get a 'Y followed you' notification when Y actually unfollowed X. Twitter has told multiple news outlets that it’s working on a fix. In the meantime, don’t unfollow anyone if you don’t want them to know.
In the meantime, you can mute the user, which will keep them out of your feed but not out of your mentions or DMs. If you get caught unfollowing, claim it was an accident or a bug (very believable!). Refollow and then mute. Or you can bite the bullet and let people know exactly what you think of them.
That also means that if you’ve been excited to see new people following you this week, they might have actually unfollowed you, so go ahead and check that. But the issue is only happening to some users, not all.