You can view the official release notes here.

Controller Changes Since 5.6.29

• Fixed blank page displaying when one double clicked on Insights.
• Fixed issues with downloading large backups over WebRTC.
• Improved reliability of UniFi cloud access service.
• Various backend bugfixes and improvements.

Controller Changes Since 5.6.26

• Improved support of Elite Device.
• Fixed issue where USW management VLAN would reset to defaults on controller upgrade.
• Added model end of life (EOL) pending warning.
• Made optimziations to drag and drop.
• Fixed missing action buttons after enabling cloud access.
• Updated nanoHD name.
• Made several device management improvements including improving the UX and mitigated some errors.
• Various backend improvements.

Controller Changes Since 5.6.22

• Fixed WLAN VLAN range.
• Fixed lost DPI translations.
• Added a tooltip to OpenVPN shared key UI.
• Now allows opening debug terminal and airTime/airView at the same time.
• Improved UI of Cloud Access Settings page.
• Fixed cloud access GUI pages for multiple super admins.
• Fixed Calendar dropdown being cut off on small screens.
• Fixed displaying Location alias on Neighboring Access Points page.
• Fixed empty tabs in property panel after adopting device in Managed by Other state.
• Fixed no DPI data for some time in users tab in traffic stats.
• Fixed remembering rows per page on Insights pages.
• Fixed selecting default Echo Server in the USG Advanced Settings.
• Fixed WiFi icon on OS X High Sierra (Chrome & Firefox).
• Set RF Scanning stat just after scan is started.
• Added elite device events to notification settings.
• Now display Default Expiration Time Field for Hotspot and Facebook WiFi.
• Disabled HTTPS redirection for Facebook, Facebook WiFi and Google.
• Fixed missing DPI users (name & icon).
• Added workaround for Cloud Key firmware upgrade issue (devices on 0.8.1 to 0.8.4).
• Various backend changes and improvements.

Controller Changes Since 5.6.20

• Enabled Custom Antenna Gain if user is Professional Installer.
• Show ‘Version’ column in AP/Switch filtered view by default.
• Added links to UniFi mobile apps on login page.
• Foxed applying custom antenna gain for US region.
• Upgrade button no longer disappears upon naming.
• Fixed map device RF button not working correctly.
• Fixed client name not showing correctly in DPI Application Usage widget.
• Fixed the guest portal and preview.
• Made security improvements.
• Updated WebRTC JNI to 1.0.27.
• Various backend improvements and bugfixes.

Controller Changes Since 5.6.19

• Official release notes are here.
• Fixed bytes to bps conversion when value is undefined.
• Fixed device name and icon missing in DPI Users view.
• Fixed pending changes icon.
• Always show the Ports tab for In-Wall APs.
• Removed port profiles for In-Wall APs.
• Fixed resetting speed test on site switch.
• Fixed incorrect dark styles for Firmware Manager.
• Updated translations.
• Made security improvements.
• Made various backend bugfixes and improvements.

Firmware Changes Since 3.9.15/4.4.12

• HD/SHD/XG
  • Stability and performance improvements.
  • Fixed a memory leak when multicast enhancements were enabled.
• AC-IW/IW-Pro/EDU/M-Pro
  • Added ability to set port negotiation.*
• nanoHD
  • Fixed MBSS support.
  • Stability improvements.
  • Added guest control support.
  • Added 802.1X support.
  • Added support for multiple BSSIDs per radio.
  • Fixed issue when using a bracket in the ESSID or PSK.
  • Fixed autochannel selection.
  • Fixed 802.11n negotiation issue.
  • Fixed issue where ethernet would stay down after provisoning/reboot.
• UAP
  • Improved STA signal reporting.
  • Improved wireless uplink/mesh V3.*
  • Fixed a bug with rate control when using multiple SSIDs.
  • Fixed NAS-IP-Address attribute which did not always return the management IP of the AP.
  • Various bugfixes and improvements.
• USW
  • Various improvements.
• USG
  • Added non-offloaded DPI support. This means DPI now functions when hardware offloading is disabled, it can now co-exist with features that disable/bypass it (smart queues, IDS/IPS).
  • GeoIP Fixes – All known problems resolved, added back end for directional control.
  • SNMP persistent directoy has been relocated to RAM disk preventing the “Unhandled kernel unaligned access” crash.
  • Removed core handling script that was causing reboots when large core files were generated.
  • Fixed IGMP proxy failing to start during boot.
  • Fixed potential issue of UPnP failing to start during boot.
  • Changed IPS loading of ipset contents to be more efficient, greatly reducing CPU usage after initial bootup and enabling of service.
  • xl2tpd package upgraded.
  • Other IDS/IPS back end improvements.
  • Fixed ubnt-cfgd zombie process issue.
  • Added SNMPv3 back end.
  • Added lock wait to all iptables operations to avoid errors in cases where multiple operations happen simultaneously.
  • Updated DPI signature.
  • Added IDS/IPS back end.
  • Fixed informs for IPv6 PD size which was causing the PD size to be cleared in the controller.
  • Added support for sending custom events to the controller.
  • Fixed DDNS update public IP checking for NATed WANs.
  • Local UI now pings ping.ubnt.com rather than default gateway for internet connectivity test.
  • Copied ‘hostname’ and ‘mailname’ over during upgrades to ensure consistency with other retained files cross-upgrade (from EdgeRouter, generally no functional impact on USG).
• USGXG
  • Made Bluetooth backend updates.
  • Improved VLAN hardware offload.
  • Problem with DHCP hardware offload fixed.
  • LCM (display) firmware update now includes splash screen and update process improvements.
• HW
  • New protocol implementation.
  • Added controller support for netconsole.*
  • Fixed some issues which caused L3 adopted devices to show up as disconnected in the controller.
  • Fixed SNMP sysName.

Firmware Changes Since 3.9.3/3.9.6

•  UAPG3
  • Made minimum rate fixes.
  • Further improvements to device upgrade and boot times.
  • Fixed a crash in hostapd when Fast Roaming is enabled.
  • Added support for 802.11r and 802.11k.
  • Fixed channel utilization reports.
  • Improved bootup and TFTP recovery times.
• UAPG2/3
  • Added RADIUS VLAN support to MAC authentication bypass.
  • Fixed a bug which prevented APs from upgrading when bandsteering was enabled.
  • Fixed bug causing 100% utilization of CPU by /bin/hostapd /etc/aaa1.cfg.
• UAPG1/2
  • Added net-snmp.
  • Added support for 802.11k.
• AC-IW/IW-Pro/Pro/EDU/M-Pro
  • Fixed VLAN passthrough regression.
  • Added port disable support.*
  • Improved VLAN config to prevent traffic leaks.
  • Fixed RADIUS VLAN when port VLAN is enabled.
  • Added QoS CIR/EIR support.
  • Improved performance.
  • Fixed management VLAN issue which caused decreased multicast perfomance.
• XG
  • Fixed airView and airTime support.
• nanoHD
  • Add stainfo support.
• EDU
  • Fixed issue with volume not applying.
  • Improved baresip config script.
• UAP
  • Fixed small memory leak.
  • Fixed outdoor flag.
  • Added fast-apply for guest portal.
  • Improved redirector handling for guest portal.
  • Fixed a bug with L3 wireless adoption.
  • Fixed bandsteering.
  • Fixed bug in bridge priority so that the secondary ethernet port remains enabled.
  • Made improvements to DFS.
  • Fixed an issue preventing bandsteering from being enabled.
  • Fixed an issue with the downlink monitor.
  • Added uplink priority for the bridge interfaces.
  • Added KRACK AP mode patches for 802.11r.
  • Made various bugfixes and improvements.
• USEW
  • Added port ID in STP error message.
  • Lowered STP topology change log level.
  • Made improvements to DHCP gaurding and snooping.
  • Added DHCP snooping debug command.
• USL2
  • Improved PSU status reporting.
• USXG
  • Improved LAG config handling.
• HW
  • Improved security.
  • Updated openssl package to 1.0.2m.
  • Udpated curl to 7.57.0.
  • Added IPv6 management support.*
  • Improved event notification on device upgrade.
• SEC
  • Fixed CVE-2017-14106.