BMW is working on an updated version of its its 5-Series, which is due out later this year as a 2021 model.

The high-performance M5 variant is also due to be updated and included in the range this time will be a new performance flagship positioned above the current M5 Competition and likely carrying the M5 CS designation. A prototype for this flagship has just been spotted.

The prototype may look like earlier testers for the updated M5 but if you look a little closer you'll notice some key differences.

2021 BMW M5 CS spy shots - Photo credit: S. Baldauf/SB-Medien

2021 BMW M5 CS spy shots - Photo credit: S. Baldauf/SB-Medien

Both the grille and front fascia are unique to this prototype. There's also a front lip spoiler not seen on earlier testers, and at the rear is a new trunk lid spoiler that matches the design used on the M2 CS, M3 CS and M4 CS.

It isn't clear what modifications are under the hood but word on the street is that the M5 CS will be the first recipient of a newly developed V-8.

The new V-8 is allegedly more compact than the current 4.4-liter V-8 that BMW uses, but still equipped with the "hot-V" turbocharger configuration and likely other attributes of the existing engine. The new engine is also thought to be electrification ready, meaning we could see some form of electrification, such as a mild-hybrid system, on the M5 CS.

2021 BMW M5 CS spy shots - Photo credit: S. Baldauf/SB-Medien

2021 BMW M5 CS spy shots - Photo credit: S. Baldauf/SB-Medien

Expect peak output to be well above the 617 horsepower of the M5 Competition, which we know is a conservatively rated figure.

Other modifications that have featured on BMW's past CS models have been reduced weight, less strict electronic nannies, and exclusive items in the cabin.

As mentioned above, the updated 5-Series is set to arrive at dealerships late this year as a 2021 model. The updated M5, including this new M5 CS, should follow shortly after.