Did you read the 1.3.0 release announcement? Rancher strongly recommends that you upgrade the Infrastructure Stacks before upgrading to 1.3.0.
I’m running Rancher 1.2, and I don’t want to upgrade until 1.3.0 has been out for a while. But I’d like to know what fixes are included when an Infrastructure Stack says “Upgrade Available” before I decide to hit the button.