Condensation on bathroom vent
The only way to fix this properly is to run an insulated pipe from the bathroom fan to the exterior of the house. The pipe should be insulated to avoid condensation buildup on the outside of the pipe. It's mostly an issue if you have cold winters, but either way, probably good practice. The best way would probably be to run it horizontally, with a slight slope away from the fan, to an outside wall (shortest route possible).

The second best option is to run it up through your roof, which would likely be more involved as you would need to install the vent flashing properly to avoid roof leaks.

The third option, if nothing else will work, would be to run it out your soffit. They make special soffit vent caps for this. This can cause the moisture to be sucked back into your attic, which is why I would go with one the first two options.

The issue with your current setup is that you are constantly blowing large amounts of moisture into your attic, where it probably just stays. This will eventually cause issues with mold, or rotting up there. If you have cellulose insulation, that will break down from the moisture as well.

You should also ensure that there is a flap at the end of the run. Some fans have one built in as well. This keeps air from going through the pipe when the fan isn't running, but gets pushed open by the fan when it is.