Showing the defects of the commodity by one of the buyers to prevent its price from rising and, thus, being able to buy it at a lower price is Haram (prohibited). In fact, this harms other Muslims, whether the commodity has defects or not. The seller should show the buyer any defects in the commodity to be acquitted of blame (Part No. 13; Page No. 118) and to avoid deception.
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.