I have a recently purchased MacBook Pro 2015. Since purchasing, I have had CPU spikes using Firefox and Chrome browsers when on Yahoo, particularly when running videos in news stories. Activity Monitor will rise to over 100% and fan gets so loud I can't use my computer. I have worked with Apple for the past 9 weeks to try to resolve, telling them that I do not have this problem on any other Apple product I currently use or have ever used since 1987, including my last Mac Book Pro (2011) and my MacBook Air at work. It is clearly something specific about *this* computer, but after 2 months of trying everything Apple has walked me through -- including having hardware tested at Apple Store, wiping computer clean, re-installing operating system, resetting PRAM and SMC, all sorts of Firefox settings tweaks (including Hardware Acceleration on and off), telling me to use Safari instead (I don't like Safari and do not want to use, though I tested it and don't have this problem using Safari, but DO have it using Chrome as well), making videos and uploading files to Apple engineers -- Apple doesn't know how to fix this. They said my next step is to contact Mozilla and have Mozilla tell me what the Apple engineers need to do to solve this problem.