Manual:$wgFileBlacklist

Details
Files with these extensions will never be allowed as uploads.

This is the default value:

  overrides  , so you must remove an extension from the blacklist before you can upload files that have it.

For instance, to allow users to upload executables, add this to :

$wgFileBlacklist = array_diff( $wgFileBlacklist, array ('html') ); $wgFileExtensions[] = 'html';