Index: branches/5.2.x/core/units/helpers/upload_helper.php
===================================================================
--- branches/5.2.x/core/units/helpers/upload_helper.php
+++ branches/5.2.x/core/units/helpers/upload_helper.php
@@ -122,7 +122,7 @@
 		$image_helper = $this->Application->recallObject('ImageHelper');
 
 		// Add extension, so that "ImageHelper::ResizeImage" can work.
-		$resize_file_path = tempnam(sys_get_temp_dir(), 'uploaded_') . '.jpg';
+		$resize_file_path = tempnam(WRITEABLE . '/tmp', 'uploaded_') . '.jpg';
 
 		if ( rename($file_path, $resize_file_path) === false ) {
 			return false;