diff --git a/app/code/core/Mage/Adminhtml/controllers/DashboardController.php b/app/code/core/Mage/Adminhtml/controllers/DashboardController.php
index ab2d654..367bf8e 100644
--- a/app/code/core/Mage/Adminhtml/controllers/DashboardController.php
+++ b/app/code/core/Mage/Adminhtml/controllers/DashboardController.php
@@ -91,9 +91,8 @@ class Mage_Adminhtml_DashboardController extends Mage_Adminhtml_Controller_Actio
         $gaHash = $this->getRequest()->getParam('h');
         if ($gaData && $gaHash) {
             $newHash = Mage::helper('adminhtml/dashboard_data')->getChartDataHash($gaData);
-            if ($newHash == $gaHash) {
-                $params = json_decode(base64_decode(urldecode($gaData)), true);
-                if ($params) {
+            if (hash_equals($newHash, $gaHash)) {
+                if ($params = unserialize(base64_decode(urldecode($gaData)))) {
                     $response = $httpClient->setUri(Mage_Adminhtml_Block_Dashboard_Graph::API_URL)
                             ->setParameterGet($params)
                             ->setConfig(array('timeout' => 5))

diff --git a/app/code/core/Mage/Adminhtml/controllers/DashboardController.php b/app/code/core/Mage/Adminhtml/controllers/DashboardController.php
index ab2d654..367bf8e 100644
--- a/app/code/core/Mage/Adminhtml/controllers/DashboardController.php
+++ b/app/code/core/Mage/Adminhtml/controllers/DashboardController.php
@@ -91,9 +91,8 @@ class Mage_Adminhtml_DashboardController extends Mage_Adminhtml_Controller_Actio
         $gaHash = $this->getRequest()->getParam('h');
         if ($gaData && $gaHash) {
             $newHash = Mage::helper('adminhtml/dashboard_data')->getChartDataHash($gaData);
-            if ($newHash == $gaHash) {
-                $params = json_decode(base64_decode(urldecode($gaData)), true);
-                if ($params) {
+            if (hash_equals($newHash, $gaHash)) {
+                if ($params = unserialize(base64_decode(urldecode($gaData)))) {
                     $response = $httpClient->setUri(Mage_Adminhtml_Block_Dashboard_Graph::API_URL)
                             ->setParameterGet($params)
                             ->setConfig(array('timeout' => 5))
diff --git a/app/code/core/Mage/Adminhtml/Block/Dashboard/Graph.php b/app/code/core/Mage/Adminhtml/Block/Dashboard/Graph.php
index da1b14a..b6d72c0 100644
--- a/app/code/core/Mage/Adminhtml/Block/Dashboard/Graph.php
+++ b/app/code/core/Mage/Adminhtml/Block/Dashboard/Graph.php
@@ -444,7 +444,7 @@ class Mage_Adminhtml_Block_Dashboard_Graph extends Mage_Adminhtml_Block_Dashboar
             }
             return self::API_URL . '?' . implode('&', $p);
         } else {
-            $gaData = urlencode(base64_encode(json_encode($params)));
+            $gaData = urlencode(base64_encode(serialize($params)));
             $gaHash = Mage::helper('adminhtml/dashboard_data')->getChartDataHash($gaData);
             $params = array('ga' => $gaData, 'h' => $gaHash);
             return $this->getUrl('*/*/tunnel', array('_query' => $params));

Basically it just reverted the 1533 and left 8788 along.