Time to apply the most recent WordPress security update.
This release should be installed for any site that is running WordPress 5.5.1 or earlier. There are 14 bug fixes as we’ll as 10 security fixes.
You can read more by looking at the release notes: https://wordpress.org/support/wordpress-version/version-5-5-2/
You can also see a complete list of changes: https://core.trac.wordpress.org/query?status=closed&resolution=fixed&milestone=5.5.2&order=priority
If you have not done so already – download the update or simply use your existing installation of WordPress to update your site. Either way – this is an excellent time to make a backup copy of your site(s) before upgrading.