Warning message exporting ListView to Excel
When user exports any ListView to Excel, Excel opens and raises a warning dialog that makes some user concerned:
This is a warning dialog, not an error message:
"The file format and extension of 'ExportData.xls' don't match. The file could be corrupted or unsafe. Unless you trust its source, don't open it. Do ypu want to open it anyway?"
Steps to Reproduce
1. Execute any ListView in User portal.
2. From the ListView results, click the "Export to Excel" button.
3. The browser raises prompt with three options: Open / Save / Cancel.
4. Click the Open button.
When user clicks the “Export to Excel” button the browser issues HTTP request to the Pega server. The invoked activity generates HTML table string
Then marks it in the HTTP response headers as an .XLS file
The XLS extension forces the browser to open Excel session. Excel in turns finds out that the content of the file is HTML table, as opposed to the expected native Excel spreadsheet format, and raises a warning to the user. Since the file comes from the trusted source, the user should safely ignore the warning and proceed with opening file.
This design supports cross-browser integration with Excel that does not require any plugins.
As explained in the "Root Cause" section this behavior is expected by design.