Is socket.assets safe in phoenix-framework?

Question

Can client (for example Phoenix Channels JavaScript client) read or write data from socket.assigns? Does by default server sign or encrypt this data?

To be more specific, here is fragment of server code:

  def join("rooms:example", _, socket) do
    socket = assign socket, :whatever, 1234
    {:ok, socket}
  end

client code:

  let socket = new Socket(SERVER_ADDR, {});
  socket.connect();
  socket.channel("rooms:example", {}).join()

is client avaible to read 1234 or change this to any other value?

Many thanks for help!