bp_document_get_allowed_extension()

function bp_document_get_allowed_extension() {
	$extensions     = array();
	$all_extensions = bp_document_extensions_list();
	foreach ( $all_extensions as $extension ) {
		if ( isset( $extension['is_active'] ) && true === (bool) $extension['is_active'] ) {
			$extensions[] = $extension['extension'];
		}
	}

	return apply_filters( 'bp_document_get_allowed_extension', $extensions );
}