i am pretty sure ( 'cos I tried it) that a forum search for amber lit will reveal the exact find / replace code needed to get rid of this specific spam.
so you can, if you like, skip understanding why it works & just type it in.
in fact , just follow the link in user-none's post & click on the spoiler button to see the code you need
this is the thread from when I was asking how to do it ~ 18 months ago:
https://www.mobileread.com/forums/showthread.php?t=75594
post 17 of that thread had the code that I needed, but yours may be slightly different.