Protecting WebGL Unity application from SendMessage exploitation

Sorry if I'm being redundant here but I couldn't find any question about this. Is there any other more secure way to call methods on my Unity WebGL appplication from browser's Javascript than using SendMessage?

I'm currently developing a web-game using SocketIO (because of its ease to use) for online multiplaying, so everytime I receive a socket event I call SendMessage to perform actions inside the game.

But, because of SendMessage being a public "user defined" function, it's easily findable and viewable its definition. This way we can easily override it with console.logs or even put a break point in its definition to track the values it receives directly from the browser's element inspector.

The thing is, anybody with a minimum knowledge in Unity WebGL development (or even web development) can hack the game by exploiting SendMessage, making the game unsecure and unfair to the rest of players.

Is there any alternative to SendMessage, or at least any way to make it more secure?

Thanks in advance.