No ledger?

Basement stairs are nailed and screwed to the walls but there is no ledger. The stringers a leaning against the floor joist. Is this a deficiency.
Pictures attached.

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Kind of hard to tell just from the photos. It’s not typical, but it looks like it would be fine, 3 nails and 2.5 drywall screws. Drywall screws (2nd photo) are not an appropriate fastener for that application. Realistically, it’s hard to imagine circumstances under which they’d fail. Maybe under a heavy impact.
Shear strength of 16d sinkers is about 900 lbs each. Those are probably 12d gun nails. I have no idea about the shear strength of drywall nails.
Mention that it’s not fastened in a typical manner, mention that drywall screws are not an appropriate fastener for that application. Maybe recommend additional fasteners be installed by a qualified contractor.

I would at least have put an A-35 under the stringer. But agree with Kenton.

That’s guys. I felt there was to much gray area here and contacted the buyer. I informed them that I would not allow this in my house and they should have it looked at by a licensed contractor.

I would have like to seen a pic of the entire stair assembly .