Ubuntu Security Notice 487-1 – It was discovered that Dovecot, when configured to use non-system-user spools and compressed folders, would allow directory traversals in mailbox names. Remote authenticated users could potentially read email owned by other users.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/57806/USN-487-1.txt
Source: https://packetstormsecurity.com/files/57806/Ubuntu-Security-Notice-487-1.html