Today, for some reason, when typing an email message in Yahoo, I am unable to place the cursor into the text, if I want to change something. What happens is, I try to place the cursor but the following letter is highlighted in blue and when I press 'space' the letter is deleted. I then have to type out the whole sentence again, sort of overwriting what I have previously written.
It's not happening on here, as I'm typing this. It's 'normal' here.
If you're on a computer isn't there a key that overwrites rather than inserts. Perhaps you need to press that button.
It's labelled as 'Insert' on mine.
Chrome appears to have cached some old data from Yahoo, which was interfering with your use of that specific website (and thus wouldn't have affected AB).