This is an archived snapshot of W3C's public bugzilla bug tracker, decommissioned in April 2019. Please see the home page for more details.
https://drafts.csswg.org/selectors-4/ has an "Issue Tracking" section with two links: "GitHub" to https://github.com/w3c/csswg-drafts/issues/, which is disabled, and "Inline In Spec" to "https://drafts.csswg.org/selectors-4/#issues-index", which also doesn't accept new issues in a straightforward way. Something in that section should link to this bug tracker.