New tabs have started opening erroneously by themselves on Firefox, opening to various advertising websites, like Carabba's restaurant, Carnival Cruise Lines. I have used Firefox for many, many years and this just started this past week. It is not accidental clicked links. It happens maybe once or twice per day, while I'm on an open tab looking up websites. I have checked my privacy settings and believe I've blocked all necessary options. I am protected by Webroot, whose scans show I am protected and aren't showing any suspect activity. Please help and thank you!