A malicious SCP server can send unexpected paths that could make the
client application override local files outside of working directory.
This could be misused to create malicious executable or configuration
files and make the user execute them under specific consequences.
This is the same issue as in OpenSSH, tracked as CVE-2019-6111.
Do not use SCP! SCP is deprecated for several years and will
be removed in future releases!
If you have to, the application MUST validate the path returned
from ssh_scp_request_get_filename() is the path the application
requested. The libssh does not do any writing in this case.