Bing Search may sometimes show a “Trending in Bing” carousel at the top of the search results. That carousel shows alternative search refinements based on your previous query but it also can contain ads.

Here is an example of it showing an ad card embedded in the other search refinements in the “Trending on Bing” section:

I spotted this via Shameem Adhikarath who posted about this on X:

Forum discussion at X.

Note: I used Bing DALL-E for this image, not MidJourney.