[kall]

It's probable that this is being caused by https://vborg.vbsupport.ru/showthread.php?t=233629 - the Author rather sneakily hid the copyright by encoding it in Base64.

PHP Code:

    if (!isset($yaexiste))
    {
        if (!$vbulletin->userinfo['userid'])
        {
            $vbphrase[unserialize(base64_decode("czoyMDoicG93ZXJlZF9ieV92YnVsbGV0aW4iOw=="))] .= '<br />Hacks por <a href="http://www.vbsoporte.com/" target="_blank">vBsoporte</a> - <a href="http://www.vbsoporte.com/foros/" target="_blank">vBulletin en Español</a>';
        }
        $yaexiste = 1;
    } 


It's in a massive plugin called Insertando Tabs that runs on the parse_templates hook.

Though, if you uninstalled the Product, that plugin should have gone too.