I've not seen this before. Looks more like visual artefacting from a graphics processing error to me on first glance.

Where was this specific ad? Might try to find one in the wild myself?

If it is a QR code it seems like maybe some kind of proprietary watermarking tech to track ads for some very specific purpose. My phone either can't lock onto it or can't read it.

What happens if you take a photo of the ad? Does it takes you to the website?

drive by exploits