In wings/internal/ufs/fs unix.go (line 92-94), this function is defined and is used to change permissions of files in the server:

func (fs *UnixFS) fchmodat(op string, dirfd int, name string, mode FileMode) error {
  return ensurePathError(unix.Fchmodat(dirfd, name, uint32(mode), 0), op, name)
}

This call to the unix function fchmodat(int fd, char* name, mode t mode, int flags) does not have the flag AT SYMLINK NOFOLLOW set, and Wings neither checks or validate if the target file is a symlink. This allows one to change permissions of files or folders outside of the server container by making symlinks to existing files in the host and then chmoding it.