Mozilla has pushed out an emergency update to Thunderbird 31.1.0 on September 24th. Thunderbird 31.1.2 addressed these issues:
Fixed an issue where anchor links would not work in HTML emails (Bug 974857)
MFSA 2014-73: RSA Signature Forgery in NSS
Depending on the users update settings, they will be prompted to install the Thunderbird Update or may do so via Help > About Thunderbird. Users can also download and manually install the latest version of Mozilla Thunderbird via getthunderbird.com site. The next scheduled update for Thunderbird will be Thunderbird 31.2.0 on October 14, 2014.