Problem with Firefox dark theme

Hi,

I run twentythirteen and got an email from a reader that had the textarea show up with black text on a dark background. He writes:

(see attached screenshot, Firefox).

This usually happens when you only set either background or foreground
color, but not both.

Looks like this is the culprit:

input, textarea {
color: #141412;
}

– style.css L578

If you add, say, background-color: white; it should be fine on both light
and dark themes.

– end of quote –

Looks like that would be a fairly simple change?