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

Here are the details from the Slackware 14.2 ChangeLog:
+--------------------------+
patches/packages/mozilla-firefox-60.5.1esr-i686-1_slack14.2.txz: Upgraded.
This release contains security fixes and improvements.
For more information, see:
https://www.mozilla.org/security/known-vulnerabilities/firefoxESR.html
https://www.mozilla.org/en-US/security/advisories/mfsa2019-05/
https://www.mozilla.org/en-US/security/advisories/mfsa2019-05/#CVE-2018-18356
https://www.mozilla.org/en-US/security/advisories/mfsa2019-05/#CVE-2019-5785
https://www.mozilla.org/en-US/security/advisories/mfsa2019-05/#CVE-2018-18335
(* 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 14.2:
ftp://ftp.slackware.com/pub/slackware/slackware-14.2/patches/packages/mozilla-firefox-60.5.1esr-i686-1_slack14.2.txz

Updated package for Slackware x86_64 14.2:
ftp://ftp.slackware.com/pub/slackware/slackware64-14.2/patches/packages/mozilla-firefox-60.5.1esr-x86_64-1_slack14.2.txz

Updated package for Slackware -current:
ftp://ftp.slackware.com/pub/slackware/slackware-current/slackware/xap/mozilla-firefox-60.5.1esr-i686-1.txz

Updated package for Slackware x86_64 -current:
ftp://ftp.slackware.com/pub/slackware/slackware64-current/slackware64/xap/mozilla-firefox-60.5.1esr-x86_64-1.txz


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

Slackware 14.2 package:
f07582bbd963c1bfc196272aafbbed10 mozilla-firefox-60.5.1esr-i686-1_slack14.2.txz

Slackware x86_64 14.2 package:
a64a420c3bc481de6cc72476807b8260 mozilla-firefox-60.5.1esr-x86_64-1_slack14.2.txz

Slackware -current package:
43791c4e45350f24ac0061203bc13964 xap/mozilla-firefox-60.5.1esr-i686-1.txz

Slackware x86_64 -current package:
72bdc9762692886e2d9033ce6561ca05 xap/mozilla-firefox-60.5.1esr-x86_64-1.txz


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

Upgrade the package as root:
# upgradepkg mozilla-firefox-60.5.1esr-i686-1_slack14.2.txz

  Mozilla-Firefox (SSA:2019-044-01) Update for Slackware