Warning: File com_booking2.zip not uploaded for security reasons!

If you see such error during Booking upgrade then follow these steps:

1. Open the file administrator/components/com_booking/models/upgrade.php for editing

2. Search for the row 399 which looks like: 

$uploaded = JFile::upload($tmp_src, $tmp_dest);

3. Improve the row to:

$uploaded = JFile::upload($tmp_src, $tmp_dest, false, true);

4. Save the file and try to upgrade again.