You have a file in a SharePoint Online library that contains a space ( ) character in the file name.
You download the file to your local computer by using the Firefox web browser.
However, after the file is downloaded, you see that the file name has been changed. Specifically, the file may be missing part of the file name after the space ( ) character, or the file name extension may be missing. For example, the file Word Document.docx is downloaded with a file name of Word.docx or Word.
This is a known issue in SharePoint Online. Microsoft is working to resolve this issue.
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