Mozilla has just released Thunderbird 2.0.0.6, an update which fixes two security issues, which are detailed in the Thunderbird 2.0.0.6 section of the Mozilla Foundation Security Advisories page. For more details see the Thunderbird 2.0.0.6 Release Notes. For those of you still using TBird 1.5 builds, TBird 1.5.0.13 should be released shortly.
Source: mozillaZine