Critical security fixes and improvements to the upgrade path from Thunderbird 2 are the key changes in Thunderbird 3.0.2, released today for Windows, Mac, and Linux.

Three security fixes, all listed as critical, address an integer overflow that caused crashes in the libtheora video library, a memory safety issue in the liboggplay media library, and crashes caused by memory corruption.

There were also changes made to the in-house upgrade from Thunderbird 2. Thunderbird 3 was released last December, but many users encountered problems including data loss and functionality bugs when upgrading. This fix released today addresses Mac users only, and prevents the e-mail client from deleting the contents of local trash sub-folders during the upgrade procedure.

The way that Thunderbird handles IMAP was also improved, as fixes were implemented for memory leaks and e-mails falsely marked as unread. The full change log can be read here.