New Facebook Ad Tracking ? #FBRedDotAd

Since 1 month i watch some weird behaviour on Facebook pages using the dark mode.
Especially on the events of FB pages i see often a red dot on the left side for half a second.
It is red with 10x10 px, PNG image, 79 bytes.
Eg this page:
The dot link is :

You see : hads-ak-prn2
So i think it is ad or some tracking.

Did anyone notice this too?