The seller must disclose faults in the item to the buyer

The seller must disclose
any faults in the item which may make it less desirable and reduce its
price. There is abundant shar’i evidence to this effect. It was narrated
that Wahb ibn ‘Aamir (may Allaah be pleased with him) said: I heard the
Prophet (peace and blessings of Allaah be upon him) say: “The Muslim is
the brother of (another) Muslim. It is not permissible for a Muslim to sell
something to his brother in which there is a fault without disclosing it to
him.” Narrated by Ahmad and Abu Dawood; classed as saheeh by al-Albaani in
Irwa’ al-Ghaleel (1321). 

And it was narrated from
Abu Hurayrah (may Allaah have mercy on him) that the Prophet (peace and
blessings of Allaah be upon him) passed by a man who was selling some
foodstuff. He put his hand in it and found that it was wet. He said:
“Whoever deceives us is not one of us.” Narrated by Muslim (101). 

And Allaah knows best.