How to remove the prompt "The file format and extension of 'abcd.afoxls' don't match. The file could be could be corrupted or unsafe. Unless you trust its source, don't open it. Do you want to open it anyway?"

Question

This is in reference to question: "How to launch Excel file in SharePoint 365 as a separate instance by default"

https://learn.microsoft.com/en-us/answers/questions/808646/how-to-launch-excel-file-in-sharepoint-365-as-a-se.html

Just in case there is no solution, I'm developing an alternative:

1. Rename my Excel xslx files in SharePoint to have the extension afoxls. Example, abcd.xlsx becomes abcd.afoxls
2. Create a .NET application "AFO Launcher" that will take the afoxls file as a parameter.
3. Do a file association of the files with extension afoxls to use the "AFO Launcher" application.
4. When the "AFO Launcher" application runs with the abcd.afoxls file as a parameter, it will spawn off the following call.
   "C:\Program Files\Microsoft Office\root\Office16\EXCEL.EXE" /x abcd.afoxls
5. The /x option is to tell Excel to create a new instance instead of running in an existing instance.

I think this would work since I tried out running the following in the command prompt and I see two Excel instances being created.

"C:\Program Files\Microsoft Office\root\Office16\EXCEL.EXE" /x abcd.afoxls
"C:\Program Files\Microsoft Office\root\Office16\EXCEL.EXE" /x abcd2.afoxls

The only problem is that every time I open the afoxls file I get the following prompt.

"The file format and extension of 'abcd.afoxls' don't match. The file could be could be corrupted or unsafe. Unless you trust its source, don't open it. Do you want to open it anyway?"

Is there a way to configure Excel to to give this prompt?

Is there an alternative solution to this?

Thanks.

Regards,

Mel Calucin

Answer 1

Hi @Mel Calucin ,
Per my research and test, please follow these steps:

1.Please go to file, and click "Options":

2.Click Trust Center >> Trust Center Settings:

3.Go to Protected View, then clear all the checkboxes:

4.Finally ,click Ok to save the changes, and restart.

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