Go to Control Panel -> Wiki -> Main -> Frontpage -> Edit -> Attachments -> Add Attachment
Chrome, Internet Explorer 9: No uploader can be seen, an empty tab is displayed
Firefox: The dynamic uploader can be seen, but there is no ability to choose the classic uploader.
At code level there are references to the classic uploader so I believe at least that one should be displayed.
LPS-32971 a fix was applied to handle FileExtensionException. That issue cannot be reproduced on trunk because of this bug.
This issue is maybe related to
LPS-29543, commit hash: 27e19157395a062c75a3daa75fc1858b73a73e7c