[extra88]

That's not correct. There is no aria-open attribute and the summary implicitly has the correct ARIA state, aria-expanded, indicating that its details element is either expanded or collapsed.

There have been bugs in its implementation, particularly in Safari and differing between mobile and desktop Safari.

[chiefalchemist]

Perhaps you’re right. What I mentioned might have been an issue that has since fade due to browser and AT updates.

Thanks for correcting me.