Same thing happened today. Three times, with in three minutes of turning on the computer, malware attack that was Avast. citing itself. I thought they were good.
My computer was sitting idle one day when Avast reported a malware attack. By idle I mean it was running Chrome and displaying a site considered safe (I think it was Google) and had been sittig that way for a half hour or so. Suddenly an Avast message popped up warining me of a malware attack. To my surprise the file that caused the warning was the Avast update file: