diff --git a/.gitmodules b/.gitmodules
index fcb5bf9c8e6..26ff2ad7415 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -25,8 +25,8 @@
 [submodule "plugins/TasksTimetable"]
 	path = plugins/TasksTimetable
 	url = https://github.com/piwik/plugin-TasksTimetable.git
-        branch = master
+    branch = master
 [submodule "plugins/LoginHttpAuth"]
 	path = plugins/LoginHttpAuth
 	url = https://github.com/piwik/plugin-LoginHttpAuth.git
-        branch = master
+    branch = master
diff --git a/core/Plugin/Manager.php b/core/Plugin/Manager.php
index 1a53da63655..e209e56166f 100644
--- a/core/Plugin/Manager.php
+++ b/core/Plugin/Manager.php
@@ -16,9 +16,9 @@
 use Piwik\Option;
 use Piwik\Plugin;
 use Piwik\Singleton;
+use Piwik\Theme;
 use Piwik\Translate;
 use Piwik\Updater;
-use Piwik\Theme;
 
 require_once PIWIK_INCLUDE_PATH . '/core/EventDispatcher.php';
 
@@ -72,12 +72,17 @@ class Manager extends Singleton
         'LeftMenu'
     );
 
-    public static function getPluginsToLoadDuringTests()
+    public function getPluginsToLoadDuringTests()
     {
-        $manager = \Piwik\Plugin\Manager::getInstance();
         $toLoad = array();
-        foreach($manager->readPluginsDirectory() as $plugin) {
-            if($manager->isPluginBundledWithCore($plugin)) {
+        foreach($this->readPluginsDirectory() as $plugin) {
+            $isPluginBundledWithCore = $this->isPluginBundledWithCore($plugin);
+            $isPluginOfficiallySupported = $this->isPluginOfficialAndNotBundledWithCore($plugin);
+
+            // Do not enable other Login plugins
+            $isPluginOfficiallySupported = $isPluginOfficiallySupported && strpos($plugin, 'Login') === false;
+
+            if($isPluginBundledWithCore || $isPluginOfficiallySupported) {
                 $toLoad[] = $plugin;
             }
         }
@@ -92,6 +97,19 @@ public function getCorePluginsDisabledByDefault()
     // If a plugin hooks onto at least an event starting with "Tracker.", we load the plugin during tracker
     const TRACKER_EVENT_PREFIX = 'Tracker.';
 
+    /**
+     * @param $pluginName
+     * @return bool
+     */
+    public function isPluginOfficialAndNotBundledWithCore($pluginName)
+    {
+        static $gitModules;
+        if(empty($gitModules)) {
+            $gitModules = file_get_contents(PIWIK_INCLUDE_PATH . '/.gitmodules');
+        }
+        return false !== strpos($gitModules, "plugins/" . $pluginName);
+    }
+
     /**
      * Update Plugins config
      *
diff --git a/core/Session.php b/core/Session.php
index 871ae1650a8..7109dd0db2f 100644
--- a/core/Session.php
+++ b/core/Session.php
@@ -39,7 +39,8 @@ public static function isFileBasedSessions()
      */
     public static function start($options = false)
     {
-        if (self::$sessionStarted
+        if (headers_sent()
+            || self::$sessionStarted
             || (defined('PIWIK_ENABLE_SESSION_START') && !PIWIK_ENABLE_SESSION_START)
         ) {
             return;
diff --git a/tests/PHPUnit/Core/ReleaseCheckListTest.php b/tests/PHPUnit/Core/ReleaseCheckListTest.php
index 86166fa1e16..85ffbef354a 100644
--- a/tests/PHPUnit/Core/ReleaseCheckListTest.php
+++ b/tests/PHPUnit/Core/ReleaseCheckListTest.php
@@ -1,5 +1,6 @@
 <?php
 use Piwik\Filesystem;
+use Piwik\Plugin\Manager;
 use Piwik\SettingsServer;
 
 /**
@@ -192,7 +193,7 @@ public function test_DirectoriesInPluginsFolder_areKnown()
             $manager = \Piwik\Plugin\Manager::getInstance();
             $disabled = in_array($pluginName, $manager->getCorePluginsDisabledByDefault());
 
-            $isGitSubmodule = false !== strpos( file_get_contents(PIWIK_INCLUDE_PATH . '/.gitmodules'), "plugins/" . $pluginName);
+            $isGitSubmodule = Manager::getInstance()->isPluginOfficialAndNotBundledWithCore($pluginName);
             $enabled = in_array($pluginName, $pluginsBundledWithPiwik) || $isGitSubmodule || $pluginName == $manager::DEFAULT_THEME;
 
             $this->assertTrue( $enabled + $disabled === 1,
@@ -302,4 +303,6 @@ private function checkFilesAreInFormat($files, $format)
             $this->fail("$format format failed for following icons $icons \n");
         }
     }
+
+
 }