Exosulfatase involved in the degradation of the glycosaminoglycans (GAGs) chondroitin sulfate (CS) and dermatan sulfate (DS). Catalyzes the hydrolysis of the 6-sulfate groups of the N-acetyl-D-galactosamine 6-sulfate units (PubMed:25002587). GAG-specific sulfatases play a key role in the persistence of the major human gut symbiont B.thetaiotaomicron in the host gastrointestinal tract (PubMed:25002587). The conversion to 3-oxoalanine (also known as C-formylglycine, FGly), of a serine or cysteine residue in prokaryotes and of a cysteine residue in eukaryotes, is critical for catalytic activity. Belongs to the sulfatase family.