CODEWITHSUNDEEP
excelfile-formatvba
Hannemaster
Hannemaster

Reputation: 52

Excel file retrieve original file extension or bypass fileformat-extension mismatch

We have a file that gets imported by a macro to extend Excel's macros functionality. This file has an extension .dll. The person who originally made this purposely changed the extension to dll to make it a bit less easy for users to just open it. All was well, but now the latest excel 2016 update gives an error "file format and extension mismatch".

which is correct. Now, in my opinion, I have 2 options.

  1. change the extension to what it originally was (which I don't know).

  2. bypass the extension/file format mismatch (which I don't know how to do and might pose a security risk).

I tried the following extensions: xla,xlam,xlsx,xlsb,xlm,xls,xll. but still get the same message.

Does anyone have a clue on how I can find out what the original file extension was?

I am not sure but the file might have been created in excel 2000 or 2007.

Upvotes: 1

Views: 161

Answers (1)

Hannemaster
Hannemaster

Reputation: 52

I found out that the issue is not with extension or file format but the problem was caused by AV/bit Defender which saw the file as a zip file started scanning inside and removed a single file inside thus causing excel to no longer recognise it as a valid file. I noticed some weird behaviour as soon as I restored quite some files from backup, AV defender started using 95% cpu. after that I went into the logs and noticed defender thinks it is a trojan.

Thanks all for your input!

Upvotes: 1

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