On Sunday, April 21, 2019 at 3:14:06 PM UTC-4, Bobby wrote:
replying to CarolinaMike, Bobby wrote:
Soffit vent works well. How would moisture get back in the attic? It blows
down and had a check valve to prevent backflow.

--
for full context, visit https://www.homeownershub.com/mainte...ok-581636-.htm

The soffits are or should be vented to allow air into the attic. Cooler
air goes in there and exits via a ridge vent or similar at the peak
to ventilate the attic.
So, if the bathroom vent is pumping out air, it's not hard to imagine
that some of it will wind up going into the attic. Is it the worst thing,
that could create a problem? I doubt it. But it might not be allowed
by current code either, IDK.