VXX is an exchange traded fund that emulates the VIX, a market volatility measure. As VIX rises, equity prices decline and as VIX declines, equity prices rise. This is evident from the decline in VXX shown in the chart, coinciding with the market rally of the past two months.
Early trading indicates a bounce-back rally, that coupled with a Fed announcement later today makes anything possible. But what this chart tells us is that something is different for the first time since mid-February. Modest new market short positions are suggested, pending confirmation of an intermediate term sell-off in the next few days.