We've prepared firmware 188.8.131.5289. Please see below for the changelog and links to the firmware binaries. I've included both changelogs, as there is only one change from 3.7.38 (and it only applies to APs). We plan to push this to at least the latest controllers in the current release branches tomorrow.
Firmware changes from 3.7.38:
[UAP] Prevent VAPs with a bad config from coming up open.
Firmware changes from 3.7.37:
[UAPG3] Enable MU-MIMO sounding.
[UAPG3] Advertise country information element.
[UAPG3] Advertise QBSS Load information element.
[UAPG3] Update powersave function.
[UAPG3] PN replay improvements.
[UAP] Enable DHCP broadcast to unicast conversion by default.
[USW] Improve device logging
[USW] Add missing FASTPATH command to clear MAC address table (non-XG models).