The tech pub team is working on the final check before publishing all the documentation including the release note. In the mean time before the documents are officially published, you can find the resolved issues below so you can assess if you would like to proceed with the online upgrade.
Resolved Issues in Build 188.8.131.52.121
Resolved an issue where the "Directed-Multicast" setting would not persist on the WLAN and Ethernet interfaces on APs. [ER-7600]
Resolved a security issue related to CLI vulnerabilities. [UN-4624]