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+.. include:: ../../Includes.txt
+
+===================================================================================
+Important: #89269 - Introduce Upgrade Wizard for invalid Backend User configuration
+===================================================================================
+
+See :issue:`89269`
+
+Description
+===========
+
+Each database record in table `be_users` stores an individual user configuration in
+the field `uc`. It is exposed during runtime in :php:`$GLOBALS['BE_USER']->uc`.
+
+In older TYPO3 versions serialized class instances of :php:`\stdClass` have been
+persisted to mentioned field - which is not possible anymore since TYPO3 v9.
+
+A corresponding upgrade wizard **"Update backend user configuration array"**
+aims to convert :php:`\stdClass` data to plain PHP arrays using scalar values.
+
+Since this upgrade wizard was introduced late with TYPO3 v9.5.11 it is suggested
+to make sure this upgrade step is executed in case a website has been updated
+before (e.g. from TYPO3 v8 to TYPO3 v9.5.1).
+
+.. index:: Backend, Database, ext:install