WordPress.org is applying automatic updates to all users who had installed WordPress. 5.8 and 3.7 to fix security issues. You probably might have received an automatic update email without you installing WordPress 5.8.3.
If your website does not support automatic updates, you should install WordPress 5.8.3 for security purposes.
The security issues were discovered by a security company Sonarsourrce. The security issues affect WordPress 5.8 and 3.7. WordPress core files that were affected are;
- upgrade.php ( in wp-admin folder)
- class-wp-tax-query.php ( in wp-includes folder)
- formatting.php ( in wp-includes folder)
- post.php ( in wp-includes folder)
- class-wp-meta-query.php ( in wp-includes folder)
This is a security update and therefore it is not expected to break any site at all.