Let's be clear: one of the best hot hatchbacks is forbidden fruit in the US: yes, we're talking about the Ford Fiesta ST. While it's no longer on sale here, in Europe the Fiesta ST was recently given a mid-cycle facelift bringing fresh styling, new interior tech, and more torque. But this may not be the only update Ford has planned for its venerable hot hatchback.

Our spies have caught Ford testing a mysterious prototype at the Nurburgring that appears to be a hotter version of the Fiesta ST. At first glance, it looks like a regular black Fiesta ST, but a closer look reveals some intriguing performance enhancements.

Since the prototype is based on the pre-facelift model, we're likely looking at a test mule for a new high-performance Fiesta ST.

We already know a more powerful hybrid version of the Puma ST is coming, so it's logical to think that an electrified Fiesta ST could also be around the corner. But unlike the Puma ST hybrid prototype that was spied tackling the Nurburgring a few weeks ago, there are no yellow stickers on the Fiesta ST prototype. This is usually a tell-tale sign of an electrified powertrain being tested.

On the other hand, this clearly isn't a stock Fiesta ST. The prototype is fitted with gold brake calipers and slotted brake discs that are not available for the regular Fiesta ST.

The dual exhaust tips also look a bit larger, as does the intercooler visible through the front spoiler. These modifications indicate there is a more powerful engine lurking under the hood. For reference, the current Fiesta ST utilizes a 1.5-liter EcoBoost three-cylinder engine rated at 197 hp and 236 lb-ft of torque. A sticker on the back suggests that BWI Group worked on the brakes and chassis. One theory is that the hotter Fiesta ST could serve as a tribute to the Fiesta WRC car, which is being replaced with the hybrid Puma WRC car in next year's WRC.