Apple released a new update for Mac on Tuesday, Dec. 19. However, you won't find a suite of new features and changes when you install the update, as you did when upgrading to macOS 14 Sonoma. Instead, the update might just save you in your next virtual meeting. According to Apple's security release notes, macOS Sonoma 14.2.1 patches one solitary WindowServer bug: "A user who shares their screen may unintentionally share the incorrect content." Yikes.
The bug affects WindowServer, the process in macOS responsible for drawing windows and other elements on your screen. Therefore, it applies to all of macOS, so it’s not app-specific. It's not clear exactly how this bug might work, but from the description alone, it seems macOS accidentally displays the wrong window when you choose to share your screen during a video call. Which window your Mac decides to show is not certain, but I imagine there are plenty of windows open on your screen you may not want to inadvertently share with clients, coworkers, or corporate.
As far as FaceTime is concerned, there are multiple ways to share your screen: You can choose to share a specific window, all the windows of a select app, multiple windows, or your entire screen at once. Ignoring the last option, it seems safe to say that relying on versions of macOS prior to 14.2.1 to share specific windows you've chosen is risky business. As the bug concerns WindowServer and not FaceTime specifically, that likely applies to all video conferencing apps and services, including Zoom and Google Meet.
If you do any kind of screen sharing for work or in your personal life, you should update your Mac as soon as you can. You might also want to look into updating your other Apple devices as well: Apple also released updates for iPhone (iOS 17.2.1 and iOS 16.7.4) and iPad (iPadOS 17.2.1 and iPadOS 16.7.4), but did not issue release notes for any of these updates. As such, we don't know exactly what bugs or security vulnerabilities each patches.
To patch this screen sharing bug, open System Settings > General > Software Update. Allow macOS to check for the latest update, then hit Update Now when macOS Sonoma 14.2.1 appears.
