Whenever a prompt window opens, the first option is highlighted in blue. Tried restarting, but the problem persisted.

I'm not sure I follow you.

If by prompt window you mean a dialogue box, typically with a choice of actions ('OK', 'Cancel', 'Apply' etc.), the default choice (i.e. the one you're most likely to want, or in some cases the safest choice) is highlighted in blue.

All that means is that you can hit the Return or Enter key to choose that, while the other choices require you to use the mouse to select them.

This is not a 'problem'; it's normal system behaviour.

Typos edited by: noondaywitch

Curious indeed! Unless it's occured with a recent update I haven't a clue.

Anybody else out there seeing this?

One way to get that blue outline is to enable "All controls" in Keyboard Shortcuts (System Preferences, Keyboard).

What do you have set in preferences?

charlie

Charlie has the what. It's not new, either.

If you didn't set that option in Sys prefs, it is likely you accidentally pressed the shortcut to enable All Controls, ctrl-F7.

The outline indicates which button has focus. You can hit tab and see this outline move. It's possible you had this set to graphite previously and it got changed to blue in System Preferences > Appearance > "Appearance: Blue"

Regards