I’m using the Newsletter plugin and have the subscription widget with the new, default, 2017 Theme.
With the theme using the Dark colour options, the newsletter widget’s “Email” field is virtually unreadable. It uses a very light gray colour for the text, and with a white background you can’t see the text.
Thank you for your report of this issue. We’ll check it. You can change the color of fields and text using the custom css you can find in the subscription panel to adjust the color for your theme.