Reproducing steps:

1. Upgrade zpoi dependency to 3.9.4
2. Export any demo page from ZK Pivottable Demo to XLS format
3. Open the file in Microsoft Excel 2007+

Results:

Excel would report a "Security Alert - Office File Validation" with the message below.

WARNING: Office File Validation detected a problem while trying to open this file.
Opening this is probably dangerous, and may allow a malicious user to take over the computer.

Note:

Security Alert does not show up when using ZPOI version prior to 3.9.4.