If the feature freeze / pre-release topics leave some time, I'd like to suggest (again) the symlink problem:
Issue 3008 provides a smaller change, that fixes the immediate problem - which is a little bigger, than it appeared initially. This makes Backdrop usable in more hosting environments.
Now there's also a "head scratching issue", issue 5190, which tries to get the big picture of FileTransfer in Backdrop, and what function checkPath() is actually supposed to cover (and what not) – and if it's really able to do what it should the way it's written. There are some concerns regarding the latter.