Technically there is latest docker image available which is pre-release 1.8.12 with several fixes in it, however as it is pre-release we’d recommend to wait for the full 1.8.12 release before upgrading.
Apart from other bugs/enhancements that will be added to 1.8.12, we will also need to make some adjustments to how we check the mysql constraints on upgrade - as for example current pre-release image will show an error about it on upgrade, that’s why I’d recommend to wait for the full release.