A hidden button in an HTML form can be submitted

Even if a button is hidden with display: none, if it has a type of submit then it will still be activated if it’s the first button in a form and a user hits enter in a form field.

So it’s a good reason to always explicitly specify the type of a button since submit is the default but most of the time you want type="button".

FYI there’s an eslint rule for this for react.