Advanced Custom Fields Pro 6.4.0.1

* Security Fix - ACF now generates different nonces for each AJAX-enabled field, preventing subscribers or front-end form users from querying other field results
* Security Fix - ACF now correctly verifies permissions for certain editor only actions, preventing subscribers performing those actions
* Security Fix - Deprecated a legacy private internal field type (output) to prevent it being able to output unsafe HTML
* Security Fix - Improved handling of some SQL filters and other internal functions to ensure output is always correctly escaped
* Security Fix - ACF now includes blank index.php files in all folders to prevent directory listing of ACF plugin folders for incorrectly configured web servers

* Fix - ACF Blocks in widget areas no longer cause a fatal error when no context is available
* Fix - ACF Blocks with no fields assigned no longer show a gap in the sidebar where the form would render

* Enhancement - Options Pages registered in the UI can now be duplicated
* Fix - ACF Block validation now correctly validates Repeater, Group, and Flexible Content fields
* Fix - ACF Block validation now correctly validates when a field is using a non-default return type
* Fix - Fields moved between field groups now correctly updates both JSON files
* Fix - Icon Picker fields now render correctly when using left-aligned labels
* Fix - Icon Picker fields no longer renders tabs if only one tab is selected for display
* Fix - Icon Picker fields no longer crash the post editor if no icon picker tabs are selected for displayed
* Fix - True/False field now better handles longer On/Off labels
* Fix - Select2 results loaded by AJAX for multi-select Taxonomy fields no longer double encode HTML entities