Apple Screen Sharing uses the older VNC remote access protocol
Apple’s screen sharing feature is built on an older remote-viewing method that was not designed with strong privacy protections in mind. If it is left exposed or set up poorly, other people may be able to view or control a Mac more easily than expected.
Who is at risk
Mac users who use screen sharing, especially at home or in small offices without careful device and network settings, are most at risk.
What to watch for
Watch for screen sharing being turned on when you did not enable it, unexpected remote access prompts, or signs that someone else is viewing or controlling your Mac.
What to do
Check your Mac’s sharing settings right away and turn off screen sharing if you do not actively need it, or restrict it only to trusted people and networks.