$_GET / query variables

To retrieve $_GET parameters in a secure way, one can use get_query_var

get_query_var( string $query_var, mixed $default_value = '' ): mixed

The parameters would have first to be added to the public query variables available to WP_Query.

add_filter( 'query_vars', 'dev__pommes' );

function dev__pomme( $qvars ) {
	$qvars[] = 'pommes';
	return $qvars;
}

Source : https://developer.wordpress.org/reference/functions/get_query_var/