Last modified: 2012-04-12 13:55:33 UTC
Mediawiki prevents you from selecting files that are not in the $wgFileExtensions array, even when $wgCheckFileExtensions is set to false. When you select the file, it clears the upload file field. Expected behaviour: When $wgCheckFileExtensions is set to false, you should be able to select any file. Occurs in Firefox and Chrome, but not IE.
Seems like another bug with the JS on the upload page, which was changed in 1.17. Note that blacklisted extensions will always fail, it's only extensions that are neither blacklisted or "preferred" that are affected by this bug or by bug 24923. *** This bug has been marked as a duplicate of bug 24923 ***