Multiple security issues have been found in Thunderbird, which may lead to the execution of arbitrary code, denial of service or attacks on encrypted emails.
For the oldstable distribution (jessie), these problems have been fixed in version 1:52.8.0-1~deb8u1.
For the stable distribution (stretch), these problems have been fixed in version 1:52.8.0-1~deb9u1.
We recommend that you upgrade your thunderbird packages.
Further information about Debian Security Advisories, how to apply these updates to your system and frequently asked questions can be found at: https://www.debian.org/security/