Errata patches for sysupgrade have been released for OpenBSD 6.5 and 6.6. A new kernel may require newer firmware images when using sysupgrade.
Binary updates for the amd64, i386, and arm64 platforms are available via the syspatch utility. Source code patches can be found on the respective errata page: https://www.openbsd.org/errata65.html https://www.openbsd.org/errata66.html
