This option can be used to exclude all file names matching the specified regexp pattern. This enables you to for example deny specific file extensions from being downloaded.

Example of usage in the config.php file

$mcFileManagerConfig['download.exclude_file_pattern'] = "/^notthis$|^notthat$/i";

Example of usage in the Web.Config file

<add key="download.exclude_file_pattern" value="/^notthis$|^notthat$/i /> 

Example of usage in a mc_access file