I got the same notification and I don't use Avast, I use a paid version of Avg which is highly regarded. Also, I did some digging about this and found out that Samsung, LG and others had keys leaked and people have been using these keys to load malware in people's devices and because this malware is using a genuine key FROM Samsung, LG, etc the malware installed by the manufacturers do not see it as a threat.
I have never had an issue with malware until I used Samsung community for which I had to "update" a samsung app and hold and behold out of the sudden, my antivirus picks it up.
A quick search under Samsung code key leak and you'll find the many sources explaining this and confirmation from Samsung that this took place with reports in December that affected devices by these leaked keys.
I don't believe in coincidences and this is far too close for comfort.