As others have mentioned there could be some concern of a pullback particularly given that the volume, although up significantly from the norm, still hasn't been large. So, this move has taken place by a few hands likely setting off the "don't want to miss the train" syndrome.

Of course, for every buyer there has to be a seller and vice versa. But my interpretation of the currently moderate volume is that the significant aspect is the absence of sellers at this point. After a move of more than 50% from the low this can be considered unusual. The low volume could be explaind from the fact alone that buyers are still wary of pushing the share price too high when buying in, but still it's advancing each day. Hence, it would still be the absence of sellers that is the main explanation for the moderate volume. And this would be a very good sign of confidence.

(I also notice the "bearish three gap ups" in the candlesticks, but intuitively yesterday's price action felt to me rather like confirming the current strength)