The OS X El Capitan…
OS X El Capitan v10.11.4
The OS X El Capitan v10.11.4 Update improves the stability, compatibility, and security of your Mac, and is recommended for all users.
OS X El Capitan v10.11.4 update :
Adds the ability to passcode-protect notes containing personal data in Notes
Adds the ability to sort notes alphabetically, by date created, or date modified in Notes
Adds the ability to import Evernote files into Notes
Adds support for sharing Live Photos between iOS and OS X via AirDrop and Messages
Addresses an issue that may cause RAW images to open slowly in Photos
Adds the ability for iBooks to store PDFs in iCloud, making them available across all your devices
Prevents JavaScript dialogs from blocking access to other webpages in Safari
Fixes an issue that prevented the VIPs mailbox from working with Gmail accounts
Fixes an issue that caused USB audio devices to disconnect
Improves the compatibility and reliability of Apple USB-C Multiport Adapters
OS X El Capitan v10.11.4 Enterprise content:
Fixes an issue that could cause a black screen after logging in as the root user
Fixes an issue that prevents using screen sharing to remotely click the Allow button or Always Allow button in Keychain Access
Fixes an issue that prevents Migration Assistant from opening when automatic login has been disabled using a configuration profile
Fixes an issue that prevents Mail from showing the date and time of certain Microsoft Exchange calendar events
Provides compatibility with the Cisco AnyConnect VPN client
Improves the reliability of connecting to a Personal Hotspot via Wi-Fi
For detailed information about the security content of this update, see Apple Security Updates.