Index: typo3/sysext/install/Classes/Updates/Base.php
===================================================================
--- typo3/sysext/install/Classes/Updates/Base.php	(Revision 10144)
+++ typo3/sysext/install/Classes/Updates/Base.php	(Arbeitskopie)
@@ -187,8 +187,38 @@
 		$res = $this->checkForUpdate($explanation, $showUpdate);
 		return ($showUpdate != 2 || $res == TRUE);
 	}
-	
 
+	/**
+	 * This method creates an instance of a connection to the Extension Manager
+	 * and returns it. This is used when installing an extension.
+	 * 
+	 * @return tx_em_Connection_ExtDirectServer EM connection instance
+	 */
+	public function getExtensionManagerConnection() {
+			// Create an instance of language, if necessary.
+			// Needed in order to make the em_index work
+		if (!isset($GLOBALS['LANG'])) {
+			$GLOBALS['LANG'] = t3lib_div::makeInstance('language');
+			$GLOBALS['LANG']->csConvObj = t3lib_div::makeInstance('t3lib_cs');
+		}
+			// Create an instance of a connection class to the EM
+		$extensionManagerConnection = t3lib_div::makeInstance('tx_em_Connection_ExtDirectServer', FALSE);
+		return $extensionManagerConnection;
+	}
+
+	/**
+	 * This method can be called to install extensions following all proper processes
+	 * (e.g. installing in both extList and extList_FE, respecting priority, etc.)
+	 *
+	 * @param array $extensionKeys List of keys of extensions to install
+	 * @return void
+	 */
+	protected function installExtensions($extensionKeys) {
+		$extensionManagerConnection = $this->getExtensionManagerConnection();
+		foreach ($extensionKeys as $extension) {
+			$extensionManagerConnection->enableExtension($extension);
+		}
+	}
+
 }
-
 ?>
Index: typo3/sysext/install/updates/class.tx_coreupdates_installsysexts.php
===================================================================
--- typo3/sysext/install/updates/class.tx_coreupdates_installsysexts.php	(Revision 10144)
+++ typo3/sysext/install/updates/class.tx_coreupdates_installsysexts.php	(Arbeitskopie)
@@ -179,33 +179,31 @@
 	 * @return	boolean		whether it worked (true) or not (false)
 	 */
 	public function performUpdate(&$dbQueries, &$customMessages) {
-		$result = false;
+		$result = FALSE;
 
-		// Get extension keys that were submitted by the used to be installed and that are valid for this update wizard:
+			// Get extension keys that were submitted by the user to be installed and that are valid for this update wizard
 		if (is_array($this->pObj->INSTALL['update']['installSystemExtensions']['sysext'])) {
 			$extArray = array_intersect(
 				$this->newSystemExtensions,
 				array_keys($this->pObj->INSTALL['update']['installSystemExtensions']['sysext'])
 			);
-			$extList = $this->addExtToList($extArray);
-			if ($extList) {
-				$this->writeNewExtensionList($extList);
-				$result = true;
-			}
+			$this->installExtensions($extArray);
+			$result = TRUE;
 		}
 
 		return $result;
 	}
 
-
 	/**
 	 * Adds extension to extension list and returns new list. If -1 is returned, an error happend.
 	 * Does NOT check dependencies yet.
 	 *
 	 * @param	array		Extension keys to add
 	 * @return	string		New list of installed extensions or -1 if error
+	 * @deprecated since TYPO3 4.5, will be removed in TYPO3 4.7 - Should not be needed anymore. Extensions should be installed directly by calling Tx_Install_Updates_Base::installExtensions()
 	 */
 	function addExtToList(array $extKeys) {
+		t3lib_div::logDeprecatedFunction();
 			// Get list of installed extensions and add this one.
 		$tmpLoadedExt = $GLOBALS['TYPO3_LOADED_EXT'];
 		if (isset($tmpLoadedExt['_CACHEFILE'])) {
@@ -226,8 +224,10 @@
 	 *
 	 * @param	string		List of extensions
 	 * @return	void
+	 * @deprecated since TYPO3 4.5, will be removed in TYPO3 4.7 - Use Tx_Install_Updates_Base::installExtensions() instead
 	 */
-	protected function writeNewExtensionList($newExtList)	{
+	protected function writeNewExtensionList($newExtList) {
+		t3lib_div::logDeprecatedFunction();
 			// Instance of install tool
 		$instObj = new t3lib_install;
 		$instObj->allowUpdateLocalConf = 1;
Index: typo3/sysext/install/updates/class.tx_coreupdates_installnewsysexts.php
===================================================================
--- typo3/sysext/install/updates/class.tx_coreupdates_installnewsysexts.php	(Revision 10144)
+++ typo3/sysext/install/updates/class.tx_coreupdates_installnewsysexts.php	(Arbeitskopie)
@@ -134,19 +134,16 @@
 	 * @return	boolean		whether it worked (true) or not (false)
 	 */
 	public function performUpdate(&$dbQueries, &$customMessages) {
-		$result = false;
+		$result = FALSE;
 
-		// Get extension keys that were submitted by the used to be installed and that are valid for this update wizard:
+			// Get extension keys that were submitted by the user to be installed and that are valid for this update wizard
 		if (is_array($this->pObj->INSTALL['update']['installNewSystemExtensions']['sysext'])) {
 			$extArray = array_intersect(
 				$this->newSystemExtensions,
 				array_keys($this->pObj->INSTALL['update']['installNewSystemExtensions']['sysext'])
 			);
-			$extList = $this->addExtToList($extArray);
-			if ($extList) {
-				$this->writeNewExtensionList($extList);
-				$result = true;
-			}
+			$this->installExtensions($extArray);
+			$result = TRUE;
 		}
 
 		return $result;
@@ -159,8 +156,10 @@
 	 *
 	 * @param	array		Extension keys to add
 	 * @return	string		New list of installed extensions or -1 if error
+	 * @deprecated since TYPO3 4.5, will be removed in TYPO3 4.7 - Should not be needed anymore. Extensions should be installed directly by calling Tx_Install_Updates_Base::installExtensions()
 	 */
 	function addExtToList(array $extKeys) {
+		t3lib_div::logDeprecatedFunction();
 			// Get list of installed extensions and add this one.
 		$tmpLoadedExt = $GLOBALS['TYPO3_LOADED_EXT'];
 		if (isset($tmpLoadedExt['_CACHEFILE'])) {
@@ -181,8 +180,10 @@
 	 *
 	 * @param	string		List of extensions
 	 * @return	void
+	 * @deprecated since TYPO3 4.5, will be removed in TYPO3 4.7 - Use Tx_Install_Updates_Base::installExtensions() instead
 	 */
-	protected function writeNewExtensionList($newExtList)	{
+	protected function writeNewExtensionList($newExtList) {
+		t3lib_div::logDeprecatedFunction();
 			// Instance of install tool
 		$instObj = new t3lib_install;
 		$instObj->allowUpdateLocalConf = 1;