FYI -- I was not running in a private browsing window, and not quitting Firefox while the download was still in progress.

I am hoping that one of the developers will be able to confirm whether or not this was a bug fixed in version 65.0.

Since writing my post above, I learned that Firefox on Android has (or had) a "feature" that deleted downloaded files along with the browsing history, so i am wondering if there was a stray "#ifndef ANDROID" that was perhaps misspelled when the previous version for Windows was built.

I doubt it's firefox it sounds more like a security software is clearing out the download. I never had this problem with previous firefox version. I am on firefox 65 Windows 10.

I have Norton Security, and I looked at the logs. There were no detections during that period; nothing quarantined. As I pointed out, the downloads were deleted immediately on quitting Firefox version 64.x. I watched the explorer window where the files were, and the second I hit the close button, poof, they disappeared. Usually, the antivirus software will take a few seconds of minutes to detect the files; or if a virus was detected, they would be deleted the moment they were saved, DURING the session, not the second it ended.

@westend, are you sure you had the option set to clear Browsing and Download History when you were running version 64?

Would any Mozilla developer who worked on the download manager between versions 64 and 65 care to comment please?

Thanks, -J

That sounds like a Security software deletion and if your browser settings didn't have any of the options to remove or delete cache, cookies, history that would come down to the security software doing this. I had previous version of firefox where none of those boxes where checked and none of my cache, cookies, history was cleared and how I know is I once did check them and my history was cleared when I closed firefox but with them uncheck nothing was deleted.