Problem was that text in status bar was white and status bar was white as well.
I've set the color and now it looks much better
<preference name="StatusBarBackgroundColor" value="#0d8ccc" />
This is because iOS was rendering white text over a white background on the status bar. The green button you saw is actually a portion of the battery level indicator.
The Apple HIG documentation (iOS Human Interface Guidelines: Bars ) shows the difference between light content and dark content status bar styles nicely -- just imagine the "white" background color (which is the default in our case) behind the two colors of text.
Once you changed the background color, the issue went away because the light content style works nicely with the color you specified. Just remember in the future that if you change the background color you might also need to switch to the default dark content status bar style as well.