Is there a solution for that issue? I have the same problem and i can say that there is no duplicate folder of Sucuri Security. This is a new installation. My WP version is 4.6. I have scanned the whole installation (htdoc directory) for the class definition. The result was: `grep -R SucuriScanSiteCheck *
wp-content/plugins/sucuri-scanner/sucuri.php: && SucuriScanSiteCheck::isDisabled()
wp-content/plugins/sucuri-scanner/sucuri.php: && SucuriScanSiteCheck::isDisabled()
wp-content/plugins/sucuri-scanner/sucuri.php: $params[‘Settings.SiteCheckStatus’] = SucuriScanSiteCheck::statusPage();
wp-content/plugins/sucuri-scanner/sucuri.php: $params[‘Settings.SiteCheckCache’] = SucuriScanSiteCheck::cachePage($nonce);
wp-content/plugins/sucuri-scanner/sucuri.php: $params[‘Settings.SiteCheckTimeout’] = SucuriScanSiteCheck::timeoutPage($nonce);
wp-content/plugins/sucuri-scanner/sucuri.php:class SucuriScanSiteCheck extends SucuriScanSettings
wp-content/plugins/sucuri-scanner/sucuri.php: if (SucuriScanSiteCheck::isDisabled()) {
`
