Readonly Attachments (RA) is an extension which causes Thunderbird to mark saved files as read-only when opening attachments. This prevents problems with users inadverantly losing work that was saved in a temporary directory. RA does not expose any user interface elements, but overrides Thunderbird’s built-in behavior when a user double-clicks an attachment or selects “Open” from the right-click menu. RA source is now available, and the installable XPI file is available from addons.mozilla.org; the Thunderbird extension page for RA is here. The current version is 0.9.