Thanks. There is only one extension in there - Amazon Assistant. Part of a report I read said:-
The infection source in this case seems to have been browsealoud DOT com, a service run by a company called Texthelp Limited.
The browsealoud site serves up JavaScript that can convert pages on your website to speech, in order to help out visitors who aren’t fluent in English, or who aren’t good at reading.
Hence my question re Javascript.