Does this memory foam mattress need a box spring or special foundation?

No box spring is required, though it works on one if the surface is solid and flat. As an 8-inch all-foam mattress it needs even, continuous support: a platform bed, slats no more than about 3 inches apart, or a bunkie board over an older box spring. A sagging or widely slatted base lets the foam flex and can create soft spots, so a firm flat foundation keeps the support core performing as measured.