NET::Ftp allows command injection in filenames

While using NET::Ftp I realised you could get command execution through "malicious" file names.

def gettextfile(remotefile, localfile = File.basename(remotefile),
                &block) # :yield: line
  f = nil
  result = nil
  if localfile
    f = open(localfile, "w") # Vulnerable code here. open("| os command","w")
  elsif !block_given?
    result = String.new
  end