Mimetype of docx changes when content is added

OS: Fedora 38
OnlyOffice: flatpak and RPM Version


  1. Start OnlyOffice
  2. Create Empty Document
  3. Save Empty Document
  4. Close OnlyOffice
  5. Open Terminal
  6. file Document1.docx
    Dokument1.docx: Microsoft Word 2007+
  7. file --mime-type Document1.docx
    Dokument1.docx: application/vnd.openxmlformats-officedocument.wordprocessingml.document
  8. Open the previous Document with OnlyOffice
  9. Type in some Text (Hello World!)
  10. Save Document
    11 close OnlyOffice
  11. file Document1.docx
    Dokument1.docx: Zip archive data, at least v2.0 to extract, compression method=store
  12. file --mime-type Document1.docx
    Dokument1.docx: application/zip

Why does OnlyOffice change the mimetype of the document to something wrong when you start adding content to the document? Which Mimetype is the correct mimetype for docx?

This also happens on the OnlyOffice DocumentServer Docker Image.

Hi @pwf

Thank you for the detailed guide!:+1:
We are checking the situation.
I will let you know when I get something.

Hi @pwf
We have reproduced the issue and added bug 63355 to our internal tracking system.

Thank you for contributing to our product. We will try to fix bug in the next versions.

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