hashing form fields to prevent tampering
If you're posting to Craft's EntriesController-&gt;saveEntry(), then it doesn't do any hash validation.

You'd need to post to a controller of your own (from a plugin or module if you're on Craft 3), then validate the data yourself like the example in the docs you linked to:

$foo = Craft::$app-&gt;request-&gt;getPost('foo');
$foo = Craft::$app-&gt;security-&gt;validateData($foo);

if ($foo !== false) {
    // data is valid
}


Then your controller would manually save the entry similar to how Craft does after your validation.