That is an error message from the Admin Page Install file reg_multi_xsell.php that you upload once to install the admin page. After this file runs it deletes itself.
If the message keeps appearing then either
You keep uploading this file?
or for some reason it cannot delete itself.
You can manually delete it from your server by deleting this file
YOUR_RENAMED_ADMIN\includes\functions\extra_functions\reg_multi_xsell.php
Bookmarks