Error on export customer

Question

I try to export customers to CSV.

I click here:

I get this error:

Log record reads:

(some values redacted)

a:5:{i:0;s:148:"Cannot send headers; headers already sent in /var/www/1/123/www/app/code/local/MP/Customfield/Block/Customer/Account/Renderer/Confirm.php, line 8";i:1;s:1193:"#0 /var/www/1/123/www/lib/Zend/Controller/Response/Abstract.php(115): Zend_Controller_Response_Abstract->canSendHeaders(true)
#1 /var/www/1/123/www/app/code/core/Mage/Core/Controller/Varien/Action.php(1066): Zend_Controller_Response_Abstract->setHeader('Pragma', 'public', true)
#2 /var/www/1/123/www/app/code/core/Mage/Adminhtml/controllers/CustomerController.php(400): Mage_Core_Controller_Varien_Action->_prepareDownloadResponse('customers.csv', Array)
#3 /var/www/1/123/www/app/code/core/Mage/Core/Controller/Varien/Action.php(418): Mage_Adminhtml_CustomerController->exportCsvAction()
#4 /var/www/1/123/www/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(254): Mage_Core_Controller_Varien_Action->dispatch('exportCsv')
#5 /var/www/1/123/www/app/code/core/Mage/Core/Controller/Varien/Front.php(172): Mage_Core_Controller_Varien_Router_Standard->match(Object(Mage_Core_Controller_Request_Http))
#6 /var/www/1/123/www/app/code/core/Mage/Core/Model/App.php(365): Mage_Core_Controller_Varien_Front->dispatch()
#7 /var/www/1/123/www/app/Mage.php(684): Mage_Core_Model_App->run(Array)
#8 /var/www/1/123/www/index.php(83): Mage::run('', 'store')
#9 {main}";s:3:"url";s:79:"/index.php/admin/abc/customer/exportCsv/key/-redacted-/";s:11:"script_name";s:10:"/index.php";s:4:"skin";s:5:"admin";}

Magento 1.9.3.4

Answer 1

The Issue is into this extension :

app/code/local/MP/Customfield

So for cross verification, disable this extension and then check the export functionality.