Read the official Contao announcements.
Contao 4.3.1 is available
by Leo Feyer – Announcements
Contao version 4.3.1 is available. The bugfix release fixes several minor back end problems with e.g. the custom layout sections or the file upload. In addition, the changes from Contao 3.5.20 have been ported.
Due to various problems we are no longer using the
bootstrap.php.cache file and the
$kernel->loadClassCache() method, therefore you have to adjust the PHP entry points in the
web/ folder accordingly (see 7b5afa97).