Updated with video:
This silver M5 CS was spotted on video on the Nurburgring (see first car up).
The F90 M5 CS has been spotted in
LCI form featuring the facelifted front end with updated fascia, headlights and grilles. The front lip seen here is new and hasn't been spotted on previous prototypes. There also appears what may be a subtle power bulge or more aggressive lines on the hood compared to the current F90 M5.
The back features an M2 and M4 CS style trunk spoiler and there may be unique rear diffuser styling.