New mozilla-thunderbird packages are available for Slackware 14.1, 14.2, and -current to fix security issues.

Here are the details from the Slackware 14.2 ChangeLog:
+--------------------------+
patches/packages/mozilla-thunderbird-45.3.0-i586-1_slack14.2.txz: Upgraded.
This release contains security fixes and improvements.
For more information, see:
http://www.mozilla.org/security/known-vulnerabilities/thunderbird.html
(* Security fix *)
+--------------------------+


Where to find the new packages:
+-----------------------------+

Thanks to the friendly folks at the OSU Open Source Lab
(http://osuosl.org) for donating FTP and rsync hosting
to the Slackware project!

Also see the "Get Slack" section on http://slackware.com for
additional mirror sites near you.

Updated package for Slackware 14.1:
ftp://ftp.slackware.com/pub/slackware/slackware-14.1/patches/packages/mozilla-thunderbird-45.3.0-i486-1_slack14.1.txz

Updated package for Slackware x86_64 14.1:
ftp://ftp.slackware.com/pub/slackware/slackware64-14.1/patches/packages/mozilla-thunderbird-45.3.0-x86_64-1_slack14.1.txz

Updated package for Slackware 14.2:
ftp://ftp.slackware.com/pub/slackware/slackware-14.2/patches/packages/mozilla-thunderbird-45.3.0-i586-1_slack14.2.txz

Updated package for Slackware x86_64 14.2:
ftp://ftp.slackware.com/pub/slackware/slackware64-14.2/patches/packages/mozilla-thunderbird-45.3.0-x86_64-1_slack14.2.txz

Updated package for Slackware -current:
ftp://ftp.slackware.com/pub/slackware/slackware-current/slackware/xap/mozilla-thunderbird-45.3.0-i586-1.txz

Updated package for Slackware x86_64 -current:
ftp://ftp.slackware.com/pub/slackware/slackware64-current/slackware64/xap/mozilla-thunderbird-45.3.0-x86_64-1.txz


MD5 signatures:
+-------------+

Slackware 14.1 package:
acbb0321bf4f2ef2105f3b3c0324d814 mozilla-thunderbird-45.3.0-i486-1_slack14.1.txz

Slackware x86_64 14.1 package:
d27666436a9848afb9a02900ebb3da4d mozilla-thunderbird-45.3.0-x86_64-1_slack14.1.txz

Slackware 14.2 package:
488e30458ee4d763fd03db4358f5c673 mozilla-thunderbird-45.3.0-i586-1_slack14.2.txz

Slackware x86_64 14.2 package:
7e914822e9941a44c2127756334029e0 mozilla-thunderbird-45.3.0-x86_64-1_slack14.2.txz

Slackware -current package:
ea8857f4785c6ad36afde27f0ec5ef6e xap/mozilla-thunderbird-45.3.0-i586-1.txz

Slackware x86_64 -current package:
758eaf6847c1af62cdaea67d01bc1be7 xap/mozilla-thunderbird-45.3.0-x86_64-1.txz


Installation instructions:
+------------------------+

Upgrade the package as root:
# upgradepkg mozilla-thunderbird-45.3.0-i586-1_slack14.2.txz

  Mozilla-thunderbird (SSA:2016-244-01) Update for Slackware