Firefox 91 will automatically save files opened after downloading in external applications in the regular "Downloads" directory, instead of a temporary directory. Recall that Firefox offers two download modes - download with saving and download with opening in the application. In the second case, the downloaded file was stored in a temporary directory, which was deleted after the session ended.
This behavior caused dissatisfaction among users who, if they needed direct access to the file, had to additionally look for the temporary directory in which the file was saved, or re-upload the data if the file had already been automatically deleted. Now it has been decided to save files opened in applications by analogy with regular downloads, which will greatly simplify such operations as sending a document to another user after it was initially opened in an office suite or copying a multimedia file to an archive after opening in a media player. In Chrome, this behavior is implemented natively.
Source: opennet.ru