Issue with uploading HTML file in Issue Galleys section

Hi, we are using OJS
I have tried to upload an HTML file (provided for by an external supplier) from the Issue Galleys section of the Issue. Apparently the system does not recognize the file or, better, it recognizes it as an XML file (although the file type is originally indicated as Firefox HTML document) and therefore does not show it correctly.

Could you please advice?
Thank you