Caps REST API post collection requests to a sensible maximum to avoid accidentally expensive API responses.
add_filter( 'rest_post_collection_params', 'wpfolks_limit_rest_posts_per_page' );
function wpfolks_limit_rest_posts_per_page( $params ) {
if ( isset( $params['per_page']['maximum'] ) ) {
$params['per_page']['maximum'] = 50;
}
return $params;
}