Mozilla has released Thunderbird 17.0.2 on January 8, 2013. Note: version numbering of Thunderbird is now going to follow that of the Thunderbird ESR branch. This updated will include minor bug and address a security issues. For organizations, Thunderbird 17.0.2esr has also been released.
Depending on your settings (Tools > Options… > Advanced > Update Tab) you will be promoted within the next the 24-48 hours to update or can manually check via Help > About Thunderbird. You can also download (though as of press it still linking to the old Thunderbird 17.0 release via getthunderbird.com and install Thunderbird 17.0.2 this way.
The next scheduled release will be Thunderbird 17.0.3 and for organization 17.0.3esr on February 19, 2013.