If I saw only the text of the supposed controversy I would instantly diagnose it as a hoax for clickbait. There are colour constancy illusions, but I will not believe that this is one of them until I see two people actually taking opposite sides.

My introduction to this illusion was walking into the office yesterday morning, and having a co-worker show me the picture on their monitor while asking what colour the dress was. The office split fairly evenly between white & gold versus blue & black, and nobody seemed to be kidding/trolling.

The weird specificity of a couple of people's experiences also suggested they were being serious. One person who originally saw white & gold, after skimming blog posts discussing/explaining the illusion, eventually said they could kiiiinda see how it could be seen as blue & black (but that could've been a social conformity effect). Another person saw the dress as white & gold on their computer screen, but saw it as visibly blue & black when viewing their screen's image through someone's smartphone, which presented it with lower brightness.

So I deem this legit. I think this illusion messes with people so successfully by turning the relatively well-known brightness/saturation illusion (as in the checker shadow illusion) into a colour illusion, by exploiting the facts that (1) very light blue looks white, (2) brown looks like yellow/gold or black depending on intensity, and (3) perceived intensity depends on the surroundings as well as the region of focus.