The security change is intended to address a weakness when using guest access. While the server may be fine not distinguishing among clients for files (and, you can imagine in the home scenario that it doesn’t matter to you which of your family members is looking at the shared folder of pictures from your last vacation), this can actually put you at risk elsewhere. Without an account and password, the client doesn’t end up with a secure connection to the server. A malicious server can put itself in the middle (also known as the Man-In-The-Middle attack), and trick the client into sending files or accepting malicious data. This is not necessarily a big concern in your home, but can be an issue when you take your laptop to your local coffee shop and someone there is lurking, ready to compromise your automatic connections to a server that you can’t verify. Or when your child goes back to the dorm at the university. The change we made removes the ability to connect to NAS devices with guest access, but the error message which is shown in build 9926 does not clearly explain what happened. We are working on a better experience for the final product which will help people who are in this situation.