Support for Istio 1.3 ends on February 14th, 2020
According to Istio's support policy, LTS releases like 1.3 are supported for three months after the next LTS release. Since 1.4 was released on November 14th, support for 1.3 will end on February 14th, 2020.
At that point we will stop back-porting fixes for security issues and critical bugs to 1.3, so we encourage you to upgrade to the latest version of Istio (1.4.6). If you don't do this you may put yourself in the position of having to do a major upgrade on a short timeframe to pick up a critical fix.
We care about you and your clusters, so please be kind to yourself and upgrade.