set value for password field is ignored

As I understood, there are a couple of possibilities to change the field value:

First:

class YourForm extends \Phalcon\Forms\Form
{
    // your logic

    // has priority 1
    public function getCustomValue($name, $entity, $data)
    {
        if ($name == 'password') return '';
    }

    // AND/OR...

    // @see https://github.com/phalcon/cphalcon/blob/master/phalcon/forms/form.zep#L621
    // has priority 2
    public function getPassword()
    {
        return '';
    }
}

Second:

class Password extends \Phalcon\Forms\Element\Password
{
    // your logic

    public function prepareAttributes($attributes = null, $useChecked = false)
    {
        $default = parent::prepareAttributes($attributes);
        return array_merge($default, ['value' => null]);
    }
}

Third (if an entity used):

class ExampleModel extends \Phalcon\Mvc\Model
{
    // your logic

    // @see https://github.com/phalcon/cphalcon/blob/master/phalcon/forms/form.zep#L595
    public function getPassword()
    {
        return '';
    }
}

The problem is:

// @see https://github.com/phalcon/cphalcon/blob/master/phalcon/forms/element.zep#L520
/** @var \Phalcon\Forms\ElementInterface $element */
$element->clear();

doesn't work like in versions < 2.x and has no effect on the entity form element. And

// @see https://github.com/phalcon/cphalcon/blob/master/phalcon/forms/element.zep#L475
$element->_value

is just a default element value with last priority and is set if no any other values given...