This change will start failing if 'filter', 'fields', 'sort' fields of findAndModify are explicitly set to null. This might need an update to existing docs.
I have some basic users in a collection created by mongoose. My program code created one incorrectly, so I went into the command line to fix it. (its not a big application). I went to use the db.colleciton.findOneAndDelete(...) first, but it deleted the wrong entry.
I was confused at first, but I didn't craft the query in the argument right to match a record, and it should have errored out. When I use the exact same query string in db.collection.findOne(...) it errors and doesn't continue, but with db.collection.findOneAndDelete(...) it does not error, and appears to delete the first record it found.