This is a big release from the OpenBSD project. Alongside a new quantum-resistant key exchange method and several important portability improvements and bug fies, probably the biggest change is the way scp(1) is handled. From the release notes:

This release switches scp(1) from using the legacy scp/rcp protocol to using the SFTP protocol by default.

Legacy scp/rcp performs wildcard expansion of remote filenames (e.g. “scp host:* .") through the remote shell. This has the side effect of requiring double quoting of shell meta-characters in file names included on scp(1) command-lines, otherwise they could be interpreted as shell commands on the remote side.

This creates one area of potential incompatibility: scp(1) when using the SFTP protocol no longer requires this finicky and brittle quoting, and attempts to use it may cause transfers to fail. We consider the removal of the need for double-quoting shell characters in file names to be a benefit and do not intend to introduce bug-compatibility for legacy scp/rcp in scp(1) when using the SFTP protocol.

Another area of potential incompatibility relates to the use of remote paths relative to other user’s home directories, for example - “scp host:~user/file /tmp”. The SFTP protocol has no native way to expand a ~user path. However, sftp-server(8) in OpenSSH 8.7 and later support a protocol extension “expand-path@openssh.com” to support this.

In case of incompatibility, the scp(1) client may be instructed to use the legacy scp/rcp using the -O flag.

If you use SSH, and that includes practically every Linux user and modern Windows Server admin now, please consider donating to the OpenBSD Foundation.