Seeing as how the photos were taken on a Disney back-lot and the building is called Westview Public Library, it would seem that these pictures are definitely from the WandaVision set. This is not to mention that the caption on the original Instagram post reveals that the project will be on Disney+ in December.
A member of the WandaVision crew posted various photos on Instagram, seemingly taken from the set of the MCU series.
The first image depicted a building with the lettering “Westview Public Library” on the front of it. The second featured the crew standing around a tent used in the production of the series.
A selfie with Halloween decorations (pumpkins and hay bales) in the background can be seen in the third photo.
Finally, there’s a large, armored military video being operated by soldiers of some sort in the last image
Whether or not this member of the production will be in hot water due to posting this is another story entirely. For what it’s worth, he has deleted his post from Instagram. Perhaps he revealed more than he was allowed to.