Why brown turbidity found in titrating KMno4 with oxalic acid?

Brown turbidity in the titration of KMnO4 with oxalic acid may be due to the formation of manganese dioxide (MnO2). This reaction occurs in acidic conditions and indicates that the end point of the titration has been reached. MnO2 is insoluble and can appear as a brown precipitate, causing turbidity in the solution.