Controller/ReviewController.php
public function validateOptIn()
    {
        $optInValue = \OxidEsales\Eshop\Core\Registry::getConfig()->getRequestParameter('rvw_oegdproptin');
        if ($this->isReviewOptInValidationRequired() && !$optInValue) {
            return false;
        }

        return true;
    }
public function validateOptIn()
    {
        $optInValue = \OxidEsales\Eshop\Core\Registry::getConfig()->getRequestParameter('rvw_oegdproptin');
        if ($this->isReviewOptInValidationRequired() && !$optInValue) {
            return false;
        }

        return true;
    }
Validate current request data, regardless if form was submitted or not

@return bool