The zip backend mounts a zip file as a browsable Fs. Go's archive/zip
does not sanitize entry names, and readZip applied path.Clean but did
not reject a cleaned name that still pointed outside the archive. A
crafted zip could make rclone copy/sync attempt writes outside the
intended destination.
Sanitize entry names with sanitize.Path - the same check used by
rclone archive extract - skipping any entry with a ".." path
component, whether separated by "/" or "\". A backslash is otherwise
kept as an ordinary character in the name, as archive extract does. It
is up to the destination backend to make names safe for its storage.
Skipped entries are logged as a single count per archive so a crafted
archive with many escaping entries cannot flood the log.