WordPress 5.5.2 was released on October 29, 200. The release included several bug and security fixes. The 5.5.2 release also included a bug that is being fixed.
WP 5.5.2 Beta Enrollment Bug
Unfortunately, it seems that websites were enrolled in the WordPress beta program after updating to WordPress 5.5.2. If you had previously enabled WordPress automatic-updates, your site would have updated to the development version 5.5.3-alpha-49449.
You can view the issue on the WordPress.org bug ticker #51679. A WordPress Core Committer commented on the ticket, saying that they have