MacBook button with blue outline in Control Center

This is most likely due the Full Keyboard Access; it fits exactly the behavior you are seeing. I can reproduce it on my end when I turn Full Keyboard Access on.

Do you see the same blue border in other applications (Safari, Mail...)? If so, that would confirm it.

You mentioned that you already checked that setting. Try turning it back on, wait a few seconds and turn it back off. Sometimes toggling a setting can reset its proper behavior.

You may also want to restart your Mac in Safe Mode: Start up your Mac in safe mode - Apple Support. In Safe Mode, wait 5 minutes for macOS to finish cleaning up (cache files...) and restart in normal mode.

Is the WiFi button the only one affected? I cannot duplicate this on my M4 Pro Macbook Pro running 26.5. I tried some Accessibility options but cannot make that border appear.

If you close all windows and set a plain, one-color desktop, does it persist?

You might try doing System Settings > WiFi and see if there are any alerts or advisories there.

To help others her know your exact laptop type, is this a:

— MacBook (discontinued 2019 and cannot run higher than macOS 13 Ventura))

— MacBook Pro

— MacBook Air

— MacBook Neo

The last three are curently in production.

That appears to me to be a normal function of the Control Center in macOS 26.6 Tahoe.

On my Mac, when I click the Control Center icon that tray of icons appears, with the Wi-Fi icon outlined. If I press the spacebar then the Wi-Fi panel opens to allow me to select a network.

If I press the Tab key, then the outline will move from the Wi-Fi icon to the next icon, and so on, through the entire group of different function icons in that popup. Eventually the highlight cycles back around to the Wi-Fi choice.

This doesn't seem to be specifically spelled out in Apple's guidance that I can find, but it makes perfect sense to me as I use the feature.

Use Control Center on Mac - Apple Support

I should have stated that I’m still on macOS Sequoia. So @D.I. Johnson”s reply is more appropriate to the issue as you seem to be using macOS Tahoe. What is odd is that @Allan Jones states that he doesn’t see the issue in macOS Tahoe 26.5.

I’m surprised that @Allan Jones doesn’t see this on their Mac. I wonder if their chosen highlight color might be gray so this may not stand out?

Also, I see I posted a typo earlier. I am actually running 26.5 Tahoe (not 26.6).

Follow up -

I have Full Keyboard Access disabled, btw.