I don't mean to divert this thread, but perhaps some similarity here.
Yesterday the frau complained that her Firefox while displaying her opening page also set two unwanted tabs for other seemingly benign sites. This was a problem to her because sometimes she would mouse click a tab and a "cookies not set" warning would pop up on that site. I was called, you know the drill <honey would you come here a minute and look at this>.
The warning was unimportant but for the life of me I couldn't figure out why she had tabs set for some site she wasn't interested in. So I ran Malware, CC cleaner checked her options for strange add ons etc. No luck. I then went into the start menu and looked for strange programs starting up. Nothing there
about 15 mins later I found that her set Home Page had a string in it that added these tabs. I simply edited the string to remove these added characters and it fixed the problem. I have never heard or encountered this before and wonder how does such a string get set in the first place
All I could guess was that when she went into options and set her home page for the current page, she must have had those tabs open as well