1. Alice publishes a post.
2. Bob shares the post.
3. Alice edits the original post, clicking "save draft"
4. Every user who sees Bob's share of Alice's post now see the draft version of Alice's post, including a warning message that it's a draft version of the post which is not publicly visible!
Drafted edits of already-published posts should obviously not be made public until the author chooses to publish them.
This should be considered a major privacy concern, particularly as content that users are specifically told is not visible is being made publicly visible, to the point that staff may want to consider disabling editing of shared posts until they can fix it.
I've just seen another post on my timeline with a great big banner declaring that it is "not publicly visible," so this has not been fixed. It remains, in my opinion, a very big privacy concern, as you are explicitly telling the user that their draft is not publicly visible even though it very much is.
saw a post with that banner too not long ago, and thought it was a funny css crime at first, but turns out it wasn't, so it definitely seems like a spicey feature to leave running in the wild like that