ARIA now allows dangling IDREFs for

• aria-controls
• aria-describedby
• aria-flowto
• aria-labelledby
• aria-owns

A dangling IDREF is still an author error for aria-activedescendant

Spec URL

https://github.com/w3c/aria/pull/2235/changes

The author MAY set either an empty value or a value that does not match the ID of another element in the same document.

These test cases should now be valid:

html-aria/misc/aria-controls-broken-idref-novalid.html
html-aria/misc/aria-describedby-broken-idref-novalid.html
html-aria/misc/aria-flowto-broken-idref-novalid.html
html-aria/misc/aria-labelledby-broken-idref-novalid.html
html-aria/misc/aria-owns-broken-idref-novalid.html

Any aria-activedescendant value that does not match an existing ID reference exactly is an author error and will not match any element in the DOM.

This test case should be an error, not a warning:
html-aria/misc/aria-activedescendant-bad-value-haswarn.html