Value of null for Controlled Input Back

Specifying the value prop on a controlled component prevents the user from changing the input unless you desire so.

In this case, you might have accidentally set value to undefined or null.

The snippet below shows this phenomenon; after a second, the text becomes editable.

ReactDOM.render(<input value="hi" />, mountNode);

setTimeout(function() {
    ReactDOM.render(<input value={null} />, mountNode);
}, 1000);