wp-includes/ms-functions.php:2190Processes the signup nonce created in signup_nonce_fields().
$resultarrayarrayfunction signup_nonce_check( $result ) { if ( ! strpos( $_SERVER['PHP_SELF'], 'wp-signup.php' ) ) { return $result; } if ( ! wp_verify_nonce( $_POST['_signup_form'], 'signup_form_' . $_POST['signup_form_id'] ) ) { $result['errors']->add( 'invalid_nonce', __( 'Unable to submit this form, please try again.' ) ); } return $result;}Introduced in MU (3.0.0). Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/ms-functions.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.