It’s the good old white text on white background. Not really a way to defend against this, except having a no-style or high contrast mode that people actually use. Maybe some warning that would trigger if text is too small, off page or has very low contrast would help?
It seems like there could be a filter so that the AI can only see the text when it’s clear that a user could read it, and it’s okay if the AI misses some text. This might involve actually rendering it, though.