diff --git a/Documentation/ApiOverview/GlobalValues/Constants/Index.rst b/Documentation/ApiOverview/GlobalValues/Constants/Index.rst
index 96359dc4fc..0c0a678082 100644
--- a/Documentation/ApiOverview/GlobalValues/Constants/Index.rst
+++ b/Documentation/ApiOverview/GlobalValues/Constants/Index.rst
@@ -69,6 +69,38 @@ Available in frontend:
     Yes
 
 
+..  index::
+    Constants; TYPO3
+..  _globals-constants-typo3:
+
+TYPO3
+-----
+
+TYPO3 still has some extension PHP script files executed in global context
+without class or callable encapsulation, namely :file:`ext_localconf.php`,
+:file:`ext_tables.php` and files within :file:`Configuration/TCA/Overrides/`.
+When those files are located within the public document root of an instance and
+called via HTTP directly, they may error out and render error messages. This can
+be a security risk. To prevent this, those files **must** have a security gate
+as first line:
+
+..  code-block:: php
+
+    <?php
+
+    defined('TYPO3') or die();
+
+    // ... your code
+
+It is defined to :php:`true` in early TYPO3 bootstrap.
+
+..  seealso::
+
+    *   :ref:`ext_localconf.php <ext-localconf-php>`
+    *   :ref:`ext_tables.php <ext-tables-php>`
+    *   :ref:`Configuration/TCA/Overrides/ <extension-configuration-tca-overrides>`
+
+
 ..  index:: Constants; Filetypes
 
 File types
diff --git a/Documentation/ExtensionArchitecture/FileStructure/ExtLocalconf.rst b/Documentation/ExtensionArchitecture/FileStructure/ExtLocalconf.rst
index 8ced1d50dc..967b968278 100644
--- a/Documentation/ExtensionArchitecture/FileStructure/ExtLocalconf.rst
+++ b/Documentation/ExtensionArchitecture/FileStructure/ExtLocalconf.rst
@@ -110,6 +110,7 @@ The skeleton of the :file:`ext_localconf.php` looks like this:
        // Add your code here
    })();
 
+Read :ref:`why the check for the TYPO3 constant is necessary <globals-constants-typo3>`.
 
 .. index:: Extension development; PageTSconfig
 
diff --git a/Documentation/ExtensionArchitecture/FileStructure/ExtTables.rst b/Documentation/ExtensionArchitecture/FileStructure/ExtTables.rst
index 08f0b5ccbd..d79d72917a 100644
--- a/Documentation/ExtensionArchitecture/FileStructure/ExtTables.rst
+++ b/Documentation/ExtensionArchitecture/FileStructure/ExtTables.rst
@@ -122,6 +122,8 @@ new records of your table to be added on Standard pages call:
       'tx_myextension_domain_model_mymodel'
    );
 
+Read :ref:`why the check for the TYPO3 constant is necessary <globals-constants-typo3>`.
+
 .. index:: Extension development; Scheduler task registration
 .. _extension-configuration-files-scheduler:
 
diff --git a/Documentation/ExtensionArchitecture/HowTo/ExtendingTca/Examples/Index.rst b/Documentation/ExtensionArchitecture/HowTo/ExtendingTca/Examples/Index.rst
index 52b6b05790..ca57dde078 100644
--- a/Documentation/ExtensionArchitecture/HowTo/ExtendingTca/Examples/Index.rst
+++ b/Documentation/ExtensionArchitecture/HowTo/ExtendingTca/Examples/Index.rst
@@ -66,6 +66,8 @@ Here's the complete code, taken from file
       'tx_examples_options, tx_examples_special'
    );
 
+Read :ref:`why the check for the TYPO3 constant is necessary <globals-constants-typo3>`.
+
 .. note::
 
    The second example :php:`tx_examples_special` only works when the