$setup->startSetup();

$insertArray = array(
            'profile_picture' => array("type" => "varchar", "label" => "Profile Picture"),
            'security_question_1' => array("type" => "int", "label" => "Security Question 1"),
            'security_question_2' => array("type" => "int", "label" => "Security Question 2"),
            'security_answer_1' => array("type" => "varchar", "label" => "Security Answer 1"),
            'security_answer_2' => array("type" => "varchar", "label" => "Security Answer 2")
          );

          foreach ($insertArray as $key => $data) {
            $customerSetup = $this->customerSetupFactory->create(['setup' => $setup]);

            $customerEntity = $customerSetup->getEavConfig()->getEntityType('customer');
            $attributeSetId = $customerEntity->getDefaultAttributeSetId();

            /** @var $attributeSet AttributeSet */
            $attributeSet = $this->attributeSetFactory->create();
            $attributeGroupId = $attributeSet->getDefaultGroupId($attributeSetId);

            $customerSetup->addAttribute(Customer::ENTITY, $key, [
                'type' => $data['type'],
                'label' => $data['label'],
                'input' => 'text',
                'required' => false,
                'visible' => true,
                'user_defined' => true,
                'sort_order' => 1000,
                'position' => 1000,
                'system' => 0,
            ]);

            $attribute = $customerSetup->getEavConfig()->getAttribute(Customer::ENTITY, $key)
            ->addData([
                'attribute_set_id' => $attributeSetId,
                'attribute_group_id' => $attributeGroupId,
                'used_in_forms' => ['adminhtml_customer'],
            ]);

            $attribute->save();
          }
            $setup->endSetup();