So, today I get new FF 55 for my laptop and noticed that Norton Toolbar in browser extensions marked yellow. I found one article about it - https://support.mozilla.org/en-US/kb/firefox-add-technology-modernizing. It seemed that Norton Toolbar won't work with FF 57 later, so I believe that Symantec solve this issue untill Mozilla releases Firefox 57. I don't want to stay without it in my favorite browser.