Old news. Better read
THIS and
THIS. As you can see, using the latest version of Avast solves it.
IMO, I think that website make a big mistake by saying it is version 4.x which has this vulnarability.
There are several versions 4.x and the latest ones do not have this problem.
Saying version 4.x has it, is only confusing for users.
They should say something like 4.6.503 or 4.6.401 and earlier.