Ubuntu Security Notice USN-817-1 – Several flaws were discovered in the rendering engine of Thunderbird. If Javascript were enabled, an attacker could exploit these flaws to crash Thunderbird.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/80512/USN-817-1.txt
Source: https://packetstormsecurity.com/files/80512/Ubuntu-Security-Notice-817-1.html