diff --git a/typo3/sysext/core/Classes/Utility/ExtensionManagementUtility.php b/typo3/sysext/core/Classes/Utility/ExtensionManagementUtility.php
index a9e62b7bedf2f16aa5cd9825bf24e8ebd167a842..ce901c5137bb6620070d8a394e2b280aad2f7a20 100644
--- a/typo3/sysext/core/Classes/Utility/ExtensionManagementUtility.php
+++ b/typo3/sysext/core/Classes/Utility/ExtensionManagementUtility.php
@@ -1023,9 +1023,11 @@ class ExtensionManagementUtility
      * @param string $group The group ('FE', 'BE', 'SYS' ...)
      * @param string $key The key of this setting within the group
      * @param string $content The text to add (include leading "\n" in case of multi-line entries)
+     * @deprecated since TYPO3 v8, will be removed in TYPO3 v9
      */
     public static function appendToTypoConfVars($group, $key, $content)
     {
+        GeneralUtility::logDeprecatedFunction();
         $GLOBALS['TYPO3_CONF_VARS_extensionAdded'][$group][$key] .= $content;
         $GLOBALS['TYPO3_CONF_VARS'][$group][$key] .= $content;
     }
@@ -1039,9 +1041,9 @@ class ExtensionManagementUtility
      */
     public static function addPageTSConfig($content)
     {
-        self::appendToTypoConfVars('BE', 'defaultPageTSconfig', '
+        $GLOBALS['TYPO3_CONF_VARS']['BE']['defaultPageTSconfig'] .= '
 [GLOBAL]
-' . $content);
+' . $content;
     }
 
     /**
@@ -1053,9 +1055,9 @@ class ExtensionManagementUtility
      */
     public static function addUserTSConfig($content)
     {
-        self::appendToTypoConfVars('BE', 'defaultUserTSconfig', '
+        $GLOBALS['TYPO3_CONF_VARS']['BE']['defaultUserTSconfig'] .= '
 [GLOBAL]
-' . $content);
+' . $content;
     }
 
     /**
@@ -1473,9 +1475,9 @@ tt_content.' . $key . $suffix . ' {
      */
     public static function addTypoScriptSetup($content)
     {
-        self::appendToTypoConfVars('FE', 'defaultTypoScript_setup', '
+        $GLOBALS['TYPO3_CONF_VARS']['FE']['defaultTypoScript_setup'] .= '
 [GLOBAL]
-' . $content);
+' . $content;
     }
 
     /**
@@ -1487,9 +1489,9 @@ tt_content.' . $key . $suffix . ' {
      */
     public static function addTypoScriptConstants($content)
     {
-        self::appendToTypoConfVars('FE', 'defaultTypoScript_constants', '
+        $GLOBALS['TYPO3_CONF_VARS']['FE']['defaultTypoScript_constants'] .= '
 [GLOBAL]
-' . $content);
+' . $content;
     }
 
     /**
diff --git a/typo3/sysext/core/Documentation/Changelog/master/Deprecation-80583-TYPO3_CONF_VARS_extensionAdded.rst b/typo3/sysext/core/Documentation/Changelog/master/Deprecation-80583-TYPO3_CONF_VARS_extensionAdded.rst
new file mode 100644
index 0000000000000000000000000000000000000000..1afc4ebe15a6cfacedf8fa691a5de3dae20a0b45
--- /dev/null
+++ b/typo3/sysext/core/Documentation/Changelog/master/Deprecation-80583-TYPO3_CONF_VARS_extensionAdded.rst
@@ -0,0 +1,33 @@
+.. include:: ../../Includes.txt
+
+====================================================
+Deprecation: #80583 - TYPO3_CONF_VARS_extensionAdded
+====================================================
+
+See :issue:`80583`
+
+Description
+===========
+
+The global array :code:`$GLOBALS['TYPO3_CONF_VARS_extensionAdded']` has been deprecated along with the method :code:`ExtensionManagementUtility::appendToTypoConfVars()`
+
+
+Impact
+======
+
+Using method :code:`appendToTypoConfVars()` throws a deprecation warning and accessing
+:code:`$GLOBALS['TYPO3_CONF_VARS_extensionAdded']` will stop working with core version 9.
+
+
+Affected Installations
+======================
+
+Extensions using :code:`$GLOBALS['TYPO3_CONF_VARS_extensionAdded']` or method :code:`appendToTypoConfVars()`
+
+
+Migration
+=========
+
+Access :code:`$GLOBALS['TYPO3_CONF_VARS']` directly.
+
+.. index:: LocalConfiguration, PHP-API
\ No newline at end of file
diff --git a/typo3/sysext/install/Classes/Controller/Action/Tool/AllConfiguration.php b/typo3/sysext/install/Classes/Controller/Action/Tool/AllConfiguration.php
index d111bc0c78d8d98d4f487009ce5bc7e92a2eed04..eccd7425780d66f0f962d787f2017e62cf36af72 100644
--- a/typo3/sysext/install/Classes/Controller/Action/Tool/AllConfiguration.php
+++ b/typo3/sysext/install/Classes/Controller/Action/Tool/AllConfiguration.php
@@ -88,6 +88,7 @@ class AllConfiguration extends Action\AbstractAction
             $data[$sectionName] = [];
 
             foreach ($GLOBALS['TYPO3_CONF_VARS'][$sectionName] as $key => $value) {
+                // @deprecated since TYPO3 v8, will be removed in TYPO3 v9. The array TYPO3_CONF_VARS_extensionAdded will be removed in v9.
                 if (isset($GLOBALS['TYPO3_CONF_VARS_extensionAdded'][$sectionName][$key])) {
                     // Don't allow editing stuff which is added by extensions
                     // Make sure we fix potentially duplicated entries from older setups