URL: https://outlook.office.com/mail/

Browser / Version: Firefox 137.0
Operating System: Windows 10
Tested Another Browser: Yes Chrome

Problem type: Something else
Description: when downloading attachments from body of emails on Firefox, Firefox is adding "UTF-8" to beginning of filename
Steps to Reproduce:
All of a sudden when I download any attachment from an email in Outlook365, Firefox (I believe) is adding "UTF-8" to the beginning of the filename. It is only happening when I click the down pointing arrow on the attachment in the body of the email and select download. If, instead, I click on the attachment name so it opens it up in a side window, then click download from there, the filename is normal and correct. I believe it just started happening today. I was on FF v135, and when I noticed the issue, I updated to FF 137.0.2 and problem is still happening. I tested Chrome and the issue does not appear to be happening there. I tried downloading files from other web pages with FF, and the issue is not happening there.

View the screenshot

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