wp_nonce for Front-End submission form not working

Question

The nonce is not working. Even if I leave out the title field, it will still submit the post. Any ideas? I just want to verify each field and if it is empty, you will get a message ("Please fill...") and back to the page, without posting anything.

function front_end_question_form() { ?>
<form id="usernotes" name="usernotes" method="post" action="">
    <div class="input-field">

    <input type="text" placeholder="Überschrift" class="fancy-input" id="title" value="<?php if ( isset( $_POST['title'] ) ) echo $_POST['title']; ?>" tabindex="1" size="40" name="title"  />       
    </div>

    <div class="input-field">

        <textarea id="description" placeholder="Notiz Inhalt" tabindex="2" name="description" cols="50" rows="6" class="fancy-input"><?php if ( isset( $_POST['description'] ) ) { if ( function_exists( 'stripslashes' ) ) { echo stripslashes( $_POST['description'] ); } else { echo $_POST['description']; } } ?></textarea>       
    </div>

    <input type="submit" value="Speichern und an meine E-Mail-Adresse senden" tabindex="6" id="submit" name="submit" class="btn btn-primary" />
    <input type="hidden" name="post-type" id="post-type" value="usernotes" />

<?php wp_nonce_field( 'notes_nonce_field' ); ?>

</form>
<?php

if($_POST){
    submit_notes_form();
}

}
add_shortcode('question','front_end_question_form');

function submit_notes_form() {

$nonce = $_REQUEST['_wpnonce'];
if ( ! wp_verify_nonce( $nonce, 'notes_nonce_field' ) ) {
  exit; // Get out of here, the nonce is rotten!
}

 else {

    // Do some minor form validation to make sure there is content
    if (isset ($_POST['title'])) {
        $title =  $_POST['title'];
    } else {
        echo 'Bitte, schreibe Überschrift';
        exit;
    }
    if (isset ($_POST['description'])) {
        $description = $_POST['description'];
    } else {
        echo 'Bitte, schreibe Notiz Inhalt ';
        exit;
    }
    // Add the content of the form to $post as an array
    $post = array(
    'post_title' => wp_strip_all_tags( $title ),
    'post_content' => $description,
    'post_status' => 'publish',         
    'post_type' => $_POST['post-type'] 
    );
    wp_insert_post($post);
$location = site_url()."/notizen/";
    echo "<meta http-equiv='refresh' content='0;url=$location' />"; exit;
} //
    }

?>

Answer 1

You missed the wp_nonce_field action name.

wp_nonce_field('submit-users-note''notes_nonce_field' );

$nonce = $_POST["notes_nonce_field"];

if ( ! isset($nonce) ! wp_verify_nonce( $nonce, 'submit-users-note' ) ) {

  exit; // Get out of here, the nonce is rotten!

}