About This HTML Issue
The type attribute on a <button> only accepts three keywords — submit, reset, and button — so any other value is rejected.
type is an enumerated attribute, not a free-form one. submit posts the form (and is what a button does when the attribute is absent), reset clears the form fields, and button does nothing on its own and is meant to be wired up with JavaScript. Anything outside that set is invalid markup, and the browser falls back to submit, so a button you expected to stay inert may submit the form instead.
If you want the default behavior, leave the attribute off or write type="submit" explicitly; if the button should not submit, use type="button".
Invalid example
<button type="default">Save</button>
Valid example
<button type="submit">Save</button>
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