This security and maintenance release introduces 14 fixes and enhancements, including changes designed to help hosts prepare users for the minimum PHP version bump coming in 5.2.
This release also includes a pair of security fixes that handle how comments are filtered and then stored in the database. With a maliciously crafted comment, a WordPress post was vulnerable to cross-site scripting.
WordPress versions 5.1 and earlier are affected by these bugs, which are fixed in version 5.1.1. Updated versions of WordPress 5.0 and earlier are also available for any users who have not yet updated to 5.1.