Upload of pictures stays in "waiting" screen forever Before uploading, in "Details", existing Categories are not shown like in BS 2.23.3 When cancelling "insert image", picture is available in File Upload Nothing is logged in database logs, php.log, httpd error.log or messages log.
Solution: It looks like this is a bug. A required dependency is not being loaded properly. As a work around you can add the following statement to your MediaWiki:Common.js page:
/* Bugfix for '"`UNIQ--nowiki-00000000-QINU`"' */ mw.loader.using( 'mediawiki.*' );