The changelog is as follows:
11 New features:
8645 Revert MySQL 5.7 minimum notice
8633 Update rateit usage to use CSS based stars
8623 Improve jQuery data lookup for various jQuery plugins
8616 Redesign initial tab HTML structure to output as the final structure
8615 Implement read date in read indicator tooltip
8614 Rewrite core JS
8612 Implement backend pre-conditioning IF showhide
8542 Database ugrader MySQL 8.0 support: bigint and smallint do not have real sizes
8539 Review default setting for "Emails Sent From" and possible no-reply@ third choice
8538 Implement PNG, WEBP, and AVIF client side resizing
8521 Improve password reset redirect to be plugin and ajax aware
20 bug-fixes:
8655 Date and datetime calendar popups do not work
8629 outputCbJs caching not working correctly
8613 Joomla 4.0 RC3: Deprecation warning at login redirect: "CAUGHT EXCEPTION: Joomla\CMS\Factory::getUser() is deprecated"
8610 Make sure that all indexes are less than 1000 bytes long in case of utf8mb4 on MyISAM MySQL 5.7.33 engine
8608 Email linebreaks sent as non-HTML in an HTML email
8606 PMS: from substitution links to users own profile instead of the actual from profile
8605 PMS: skip converting linebreaks if an editor is used
8595 Backport PHPMailer security fixes (not exploitable in CB and add-ons)
8583 CBuser usages returning null when object is expected
8565 CB Select multiselect inputs won't let you remove all selections
8557 Guzzle declaring optional parameters before required parameters
8544 Client side resizing isn't strictly checking allowed extensions
8543 Very old unconfirmed accounts cannot be confirmed with the old confirm link
8541 Database checker: Minor regex improvement and fatal error substitution fix
8536 Uninstalling plugin with file permissions error results in fatal php exception error instead of displaying the warnings
8522 Nightly regression: CB admin configuration planel not loading Imagick version test missing a namespace backslash in the Imagick::GetVersion() call
8520 Safari transparent issue with tab navigation more button
8518 PHP 8 has a few compatibility issues due to deprecated behavior
8510 Bootstrap 3 collapse class conflicts with new navbar usage
8509 PMS avatars not sized correctly
More details at the forge tracker:
forge.joomlapolis.com/projects/cb/issues?query_id=186