I'm using Firefox 126.0.1 (64-bit) in Windows 11. I needed to download two files named index.html (in different source directories) from my company's content management system. Both got downloaded as index.htm. They were the right files... only the extension was changed. I spoke to the person who maintains the content management system. They tested it and said it's not doing that, must be the browser. That sounds fantastic to me, but I looked through the support messages here and found several about files whose extensions were changed on download; for example from .loa to .mp3. No explanations or workarounds, though. Can anyone shed light on this?