Extending a Controller

Extending "Mage_Review_ProductController"

app/code/local/Primera/Review/etc/config.xml

<config>
    <frontend>
        <routers>
            <review>
                <args>
                    <modules>
                        <primera_review before="Mage_Review">Primera_Review</primera_review>
                    </modules>
                </args>
            </review>
        </routers>
    </frontend>
</config>

app/code/local/Primera/Review/controllers/ProductController.php

<?php
require_once 'Mage/Review/controllers/ProductController.php';

class Primera_Review_ProductController extends Mage_Review_ProductController
{
    /**     * Crops POST values     * @param array $reviewData     * @return array     */

    protected function _cropReviewData(array $reviewData)
    {
        $croppedValues = array();
        $allowedKeys = array_fill_keys(array('detail', 'title', 'nickname','email'), true);

        foreach ($reviewData as $key => $value) {
            if (isset($allowedKeys[$key])) {
                $croppedValues[$key] = $value;
            }
        }

        return $croppedValues;
    }
}