Fatal error: Uncaught Error: Class "ilHtmlPurifierAbstractLibWrapper" not found in /var/www/html/ilias/components/ILIAS/Exercise/classes/class.ilExcInstructionPurifier.php:21 Stack trace: #0 {main} thrown in /var/www/html/ilias/components/ILIAS/Exercise/classes/class.ilExcInstructionPurifier.php on line 21