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.Part files are deleted. As far as I know, I have never seen one in a temp folder before/ever. Or it is converted to the finished file name. Firefox will automatically remove that .part addition once the download has finished. If the download is stopped it may be possible to resume from the .part file. That is part (no pun) of why it is created.

Please let us know if this solved your issue or if need further assistance.

The problem is that even when browsing in private mode the download is forensically unsafe since the downloaded data still exists on the hard drive after it is deleted. The solution to this problem is for Firefox to rename the .part file to the downloaded file name OR copy the .part file to the actual file then wipe the .part file. Until this is accomplished Firefox has a very usefull forensic exploit weakness that I will inform the forensic forums of immediately.

By the way you are messaging with Firefox Volunteer Support, we are not staff.

.Part files are deleted. As far as I know, I have never seen one in a temp folder before/ever. Or it is converted to the finished file name like a lot of programs do.

May want to go here and find out more : https://support.mozilla.org/en-US/kb/where-go-developer-support