Bug/Issue Strange square around lights in the mine.

So far I've only noticed this in the mines with the torches that have the breathe in and out effect, but I'm not sure what's causing it. Anyone else seen this issue? The square outline moves with the light effect.




Here's a gif of it in action

 

The gif you posted shows you're using a custom interface mod. It looks like part of the transparency may have been colored causing those lighting glitches you see.
Restoring a vanilla "Content/LooseSprites/Cursors.xnb" to your gamedata would fix that; else try messaging the modder for an update.