I guess the problem is not only affecting the text cursor...
In Microsoft Edge I had a map and when I hovered over it the cursor changed to the open hand where I could drag the map around.
And there the hand was completely white, without the black boarder.
So I think there is no problem with the color of the cursor, but the bug is, that sometimes the black border of the cursor is displayed white (or just not showing?).
And with the text cursor (which is more or less just a border) the bug is more obvious.
@Microsoft: PLS FIX THAT SH*T
EDIT: In Microsoft Edge it is more or less reproducable by having multible tabs open and then changing the tab (by clicking on it) an then dragging the mouse to the adress bar. Sadly it is not really deterministic from what I can see