Technically, the WRX and STI are based on the Impreza; but for the 2013 model year (and last year, too), they're built on quite different versions of the same architecture and although it's likely that the Impreza's excellent safety ratings and Top Safety Pick status do carry over to these models, we can't officially do so.
Standard safety equipment includes front, side, and side-curtain airbags; electronic stability and traction control; anti-lock brakes with brake-force distribution and brake assist; hill-start assist; and daytime running lamps. And of course, all WRX and STI models get Subaru's standard all-wheel drive for excellent inclement weather ability.
For the most part, the safety features in the WRX and STI mirror those of the Impreza lineup; though they do lack the new driver's knee bag that those non-performance models get.
Neither the NHTSA (National Highway Traffic Safety Administration) nor the IIHS (Insurance Institute for Highway Safety) has crash-tested an STI or WRX in recent years.