Emissive light sources have always shown in mirrors - it’s a long-term item on the wish-list.
In theory it shouldn’t be too much of a problem if you are placing light sources where there are actually lights - it becomes a problem when you try to use ‘fill-in’ lighting rather than lighting a scene more naturally (Which is what Enscape is aiming for).
Only way to “fix” it for static images is to put some decoration in the way of the reflection or erase the spots in post-production. In a ‘live’ walk-through you just have to try and set the scene with this in mind and avoid lingering at mirrors.
Hey @jaeyoungkk , thanks a lot for your post. 
This is a normal behavior and there is currently no way to turn off light sources being visible in reflections. You could also, besides @Gadget_1 's tips, reduce the “Light Source Radius” through our Enscape Objects dialogue, as this also reduces the size of the source in the reflection.
We generally have a feature request filed on our agenda to allow you to disable lightsource reflections - I’ll happily upvote that story through your behalf!
