Index: tests/t3lib/t3lib_extmgmTest.php
===================================================================
--- tests/t3lib/t3lib_extmgmTest.php	(Revision 10478)
+++ tests/t3lib/t3lib_extmgmTest.php	(Arbeitskopie)
@@ -41,6 +41,7 @@
 
 	public function setUp() {
 		$this->globals = array(
+			'TYPO3_CONF_VARS' => serialize($GLOBALS['TYPO3_CONF_VARS']),
 			'TYPO3_LOADED_EXT' => serialize($GLOBALS['TYPO3_LOADED_EXT']),
 			'TCA' => serialize($GLOBALS['TCA']),
 		);
@@ -472,5 +473,30 @@
 			t3lib_extMgm::getExtensionVersion($extensionKey)
 		);
 	}
+
+	/**
+	 * @test
+	 */
+	public function getEnabledExtensionListConsidersRequiredExtensions() {
+		$testrequiRedExtension = uniqid('test');
+		$GLOBALS['TYPO3_CONF_VARS']['EXT']['requiredExt'] = $testrequiRedExtension;
+
+		$extensions = explode(',', t3lib_extMgm::getEnabledExtensionList());
+		$this->assertTrue(in_array($testrequiRedExtension, $extensions));
+	}
+
+	/**
+	 * @test
+	 */
+	public function getEnabledExtensionListConsidersRequiredAndIgnoredExtensions() {
+		$testRequiredExtension = uniqid('test');
+		$testIgnoredExtension = uniqid('test');
+		$GLOBALS['TYPO3_CONF_VARS']['EXT']['requiredExt'] = $testRequiredExtension . ',' . $testIgnoredExtension;
+		$GLOBALS['TYPO3_CONF_VARS']['EXT']['ignoredExt'] = $testIgnoredExtension;
+
+		$extensions = explode(',', t3lib_extMgm::getEnabledExtensionList());
+		$this->assertTrue(in_array($testRequiredExtension, $extensions));
+		$this->assertFalse(in_array($testIgnoredExtension, $extensions));
+	}
 }
 ?>
\ No newline at end of file
Index: t3lib/config_default.php
===================================================================
--- t3lib/config_default.php	(Revision 10478)
+++ t3lib/config_default.php	(Arbeitskopie)
@@ -22,6 +22,9 @@
 //Security related constant: Comma separated list of file extensions that should be registered as php script file extensions
 define('PHP_EXTENSIONS_DEFAULT', 'php,php3,php4,php5,php6,phpsh,inc,phtml');
 
+// Defines a list that are basically required by a TYPO3 system.
+define('REQUIRED_EXTENSIONS', 'cms,lang,sv,em,recordlist');
+
 $TYPO3_CONF_VARS = array(
 	'GFX' => array(		// Configuration of the image processing features in TYPO3. 'IM' and 'GD' are short for ImageMagick and GD library respectively.
 		'image_processing' => TRUE,				// Boolean: Enables image processing features. Disabling this means NO image processing with either GD or IM!
@@ -171,7 +174,8 @@
 		'em_wsdlURL' => 'http://typo3.org/wsdl/tx_ter_wsdl.php',				// The SOAP URL for uploading extensions to the TER2. Usually doesn't need to be changed.
 		'em_mirrorListURL' => 'http://repositories.typo3.org/mirrors.xml.gz',				// Allows to preset the URL for fetching the extension repository mirror list from. Used in the Extension Manager.
 
-		'requiredExt' => 'cms,lang,sv,em,recordlist',		// String (exclude). List of extensions which are REQUIRED and cannot be unloaded by the Extension Manager!
+		'requiredExt' => '',		// String. List of additional extensions which are REQUIRED and cannot be unloaded by the Extension Manager!
+		'ignoredExt' => '',			// String. List of extensions to be ignored (not loaded), e.g. "em" can be disabled this way.
 		'excludeForPackaging' => '(CVS|\..*|.*~|.*\.bak)',		// String: List of directories and files which will not be packaged into extensions nor taken into account otherwise by the Extension Manager. Perl regular expression syntax!
 		'extCache' => 1,						// <p>Integer (0, 1, 2, 3)</p><dl><dt>0</dt><dd>ext-scripts (ext_localconf.php and ext_tables.php) are NOT cached, but included every time</dd><dt>1</dt><dd>scripts cached to typo3conf/temp_CACHED_[sitePathHash]* (saves some milliseconds even with PHP accelerators)</dd><dt>2</dt><dd>scripts cached and prefix includes a hash based on the 'extList' string</dd><dt>3</dt><dd>scripts cached to typo3conf/temp_CACHED_* (no hash included at all...)</dd></dl>
 		'extList' => 'filelist,version,tsconfig_help,context_help,extra_page_cm_options,impexp,belog,about,cshmanual,aboutmodules,setup,opendocs,install,t3editor,felogin,feedit,recycler',						// String (exclude) List of extensions which are enabled for this install. Use the Extension Manager (EM) to manage this!
Index: t3lib/class.t3lib_extmgm.php
===================================================================
--- t3lib/class.t3lib_extmgm.php	(Revision 10478)
+++ t3lib/class.t3lib_extmgm.php	(Arbeitskopie)
@@ -1589,10 +1589,46 @@
 			$extLoadInContext = $GLOBALS['TYPO3_CONF_VARS']['EXT']['extList'];
 		}
 
-		$extensionList = $GLOBALS['TYPO3_CONF_VARS']['EXT']['requiredExt'] . ',' . $extLoadInContext;
+		$extensionList = self::getRequiredExtensionList() . ',' . $extLoadInContext;
+		$ignoredExtensionList = self::getIgnoredExtensionList();
 
+			// Remove the extensions to be ignored:
+		if ($ignoredExtensionList && (defined('TYPO3_enterInstallScript') && TYPO3_enterInstallScript) === FALSE) {
+			$extensions = array_diff(
+				explode(',', $extensionList),
+				explode(',', $ignoredExtensionList)
+			);
+			$extensionList = implode(',', $extensions);
+		}
+
 		return $extensionList;
 	}
+
+	/**
+	 * Gets the list of required extensions.
+	 *
+	 * @return string
+	 */
+	public static function getRequiredExtensionList() {
+		$requiredExtensionList = t3lib_div::uniqueList(
+			REQUIRED_EXTENSIONS . ',' . $GLOBALS['TYPO3_CONF_VARS']['EXT']['requiredExt']
+		);
+
+		return $requiredExtensionList;
+	}
+
+	/**
+	 * Gets the list of extensions to be ignored (not to be loaded).
+	 *
+	 * @return string
+	 */
+	public static function getIgnoredExtensionList() {
+		$ignoredExtensionList = t3lib_div::uniqueList(
+			$GLOBALS['TYPO3_CONF_VARS']['EXT']['ignoredExt']
+		);
+
+		return $ignoredExtensionList;
+	}
 }
 
 ?>