Source

File: wp-includes/functions.php

function get_allowed_mime_types( $user = null ) {
	$t = wp_get_mime_types();

	unset( $t['swf'], $t['exe'] );
	if ( function_exists( 'current_user_can' ) ) {
		$unfiltered = $user ? user_can( $user, 'unfiltered_html' ) : current_user_can( 'unfiltered_html' );
	}

	if ( empty( $unfiltered ) ) {
		unset( $t['htm|html'], $t['js'] );
	}

	/**
	 * Filters list of allowed mime types and file extensions.
	 *
	 * @since 2.0.0
	 *
	 * @param array            $t    Mime types keyed by the file extension regex corresponding to those types.
	 * @param int|WP_User|null $user User ID, User object or null if not provided (indicates current user).
	 */
	return apply_filters( 'upload_mimes', $t, $user );
}