Custom domain users are reporting that traffic to their blog's Blogspot URL is inserting a redirect warning notifying users that they are leaving Blogger. Previously, no warning was issued and visits to the Blogspot URL were automatically re-routed to the user's Custom Domain.
Blogger engineers are aware of the issue and are working on a fix. We apologize for the issue, and will update this post when it is fixed.
Update, 6/22: This has been fixed.