Thunderbird stores temporary files (included decrypted attachements) indefinitely

Thunderbird is storing attachements that the user wanted to ‘open’ without ‘downloading’ them, and the content of the clipboard, in /home/amnesia/.thunderbird/profile.default/tmp/, and never erase them (I found files created in september in here).

At least, I think that Thunderbird should not keep those files from one session to another, and that encrypted attachements should not be stored in clear, even until the end of the session.

Feature Branch: bugfix/13340-clean-thunderbird-tmp-dir

Related issues

Blocks #13234 (closed)

Original created by @goupille on 13340 (Redmine)

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