Source

File: wp-includes/rest-api/endpoints/class-wp-rest-plugins-controller.php

protected function check_read_permission( $plugin ) {
		if ( ! $this->is_plugin_installed( $plugin ) ) {
			return new WP_Error( 'rest_plugin_not_found', __( 'Plugin not found.' ), array( 'status' => 404 ) );
		}

		if ( ! is_multisite() ) {
			return true;
		}

		if ( ! is_network_only_plugin( $plugin ) || is_plugin_active( $plugin ) || current_user_can( 'manage_network_plugins' ) ) {
			return true;
		}

		return new WP_Error(
			'rest_cannot_view_plugin',
			__( 'Sorry, you are not allowed to manage this plugin.' ),
			array( 'status' => rest_authorization_required_code() )
		);
	}