Mozilla released an update for the Thunderbird 24.x branch on February 4th, 2014. Thunderbird 24.3.0 addressed these issues:

• Security fixes can be found here

• Improved handling of reply-to (bug 933555)

Depending on update settings, users should automatically be prompted to update to Thunderbird 24.3.0 or may do so manually via Help > About Thunderbird or downloading and installing via the getthunderbird.com site. The next scheduled update will be Thunderbird 24.4.0.