Hi,
Yes, I was afraid that because it popped up during search results page that it could've infected my PC or router (which is password protected, not default password). So I decided to block any further attempts on router level.
That's right, KIS will not update while the word is blacklisted. It doesn't stay at 0 but downloads extremely slowly and eventually fully stops with error message "Network failure while downloading updates".
I haven't done factory reset on router as it takes awhile to set up from scratch and I currently don't have anybody who could help. :(
No, I haven't reset KIS to default settings but I haven't touched its settings to begin with, only to set it to update at a certain time.
I will look into how to make system restore point and do that.
I was afraid of this java script because one day before it happened, mum's PC - which shares my network - got some kind of adware. It would present her with a pop up ad window on safe websites (vk, facebook), with Adblock enabled. Perhaps the same java script is to blame? Although I haven't visited any of the sites she did. I purged all cache, cookies and temp folders and the problem has stopped. Her PC runs different older version of KIS as the PC itself is older. I don't know if this information is of any help though.