Modify html before submitting form: prevent this hack

Question

I came to a realization that malicious users can modify the html of a form in their browser before submitting a form. For example, switching the names of two input fields of the same types.

I am creating a website that's largely dependent upon relationships between each entries in the database.

If this happens, it could jeopardize all functions of my sites. (I've tested it, and it does switched the inputs from the two fields who names are switched in the browser by the user, ie. me)

How could we prevent this?

Answer 1

If this kind of hack causes problem on the server side, you cannot fix it in your browser code. It means that you need to fix this on the server.

Anyone can generate any kind of POST or GET to your server, and you need to be prepared for that.

So, make sure that you detect this kind of tampering on the server, and deal with it there, by returning an error message, or by silently ignoring such invalid requests.

If the server is prepared for this, you can let people hack away in their browser as much as they want.