Apple released Security Update 2019-004 (Sierra) and Security Update 2019-004 (High Sierra) on Monday. Both updates contain security patches also found in macOS Mojave 10.14.6.
[Update: Links to Sierra download updated.]
Patch Notes for Security Update 2019-004 (Sierra)
Security Update 2019-004 is recommended for all users and improves the security of macOS. For more information on the security content of this update see: http://support.apple.com/kb/HT201222
Security Update 2019-004 (Sierra) is a 927.6MB download. You can also install it through Software Update on your Mac running Sierra.
Patch Notes for Security Update 2019-004 (High Sierra)
Security Update 2019-004 is recommended for all users and improves the security of macOS. For more information on the security content of this update see: http://support.apple.com/kb/HT201222
Security Update 2019-004 (High Sierra) is a 1.9GB download. You can also install it through Software Update on your Mac running Sierra.
Security Update for Sierra hereinabove is for High Sierra.
Thanks! Both links to the Sierra download have been corrected. ☺️