Hi,
It was present in 2.3.0 and the bug, plus fix, is described here:
https://magento.stackexchange.com/questions/256223/how-to-install-magento-2-3-on-windows-10-x64-with...
With 2.3.1 the contents of that file appear to have had the fix applied, but the pattern is still the same rendering both the front and back ends totally useless.
