I get the same issue coming up when I do an Avast scan.
I had a Mac repair do it and he said that because a Malwarebytes' scan doesn't come with anything, it is not a trojan/adware/malware.
In fact, he looked manually through my launch agents to see if anything dodgy is running in the background and it was not.
His advice is to contact Avast to resolve this issue.
Hopefully that can be done sooner rather than later!