Backport-issue-195196

Author: Nazar65

app/code/Magento/Eav/Model/Attribute/Data/File.php

@@ -146,7 +146,7 @@ protected function _validateByRules($value)
             return $this->_fileValidator->getMessages();
         }
 
-        if (!empty($value['tmp_name']) && !is_uploaded_file($value['tmp_name'])) {
+        if (!empty($value['tmp_name']) && !file_exists($value['tmp_name'])) {
             return [__('"%1" is not a valid file.', $label)];
         }
 

app/code/Magento/Ui/view/base/web/js/form/element/file-uploader.js

@@ -14,7 +14,8 @@ define([
     'Magento_Ui/js/lib/validation/validator',
     'Magento_Ui/js/form/element/abstract',
     'mage/translate',
-    'jquery/file-uploader'
+    'jquery/file-uploader',
+    'mage/adminhtml/tools'
 ], function ($, _, utils, uiAlert, validator, Element, $t) {
     'use strict';
 

app/code/Magento/Variable/view/adminhtml/web/variables.js

@@ -9,7 +9,8 @@ define([
     'mage/translate',
     'Magento_Ui/js/modal/modal',
     'jquery/ui',
-    'prototype'
+    'prototype',
+    'mage/adminhtml/tools'
 ], function (jQuery, $t) {
     'use strict';