Purchased Property and later on found that the seller enter sale agreement with third party

I have purchased property and registered sale deed . Later on after one month received a court summon and came to know that the seller had earlier enterinto agreement of sale (unregistered) with another person and that person gave a very small amount of only 8% of the total contract value, so the seller didnot sale to him and he sold to me. Seller didnot disclose this to me. I came to know only when i receive court notice. The agreement holder filed case for specific performance of contract. Important points to note:- 1. Seller didnot disclose to me the earlier litigation at any point of time till i receive court notice 2.The agreement holder paid only a small amount of 8% during the 3 months time allowed by seller 3. The earlier agreement was for 3 months; But the wording in the agreement is " balance amount is payable with in 3 months or at the time of registration" based on this the agreement holder is claiming that TIME IS NOT THE ESSENCE of the Contract. 4. seller sent the cancellation notice through lawyer after receiving the advance money and entering into sale agreement with me. which he didnot told me. 5. when i purchased the property , the property documents were with Bank and the seller cleared the amount through the advance amount i have paid. I have the letter from bank. Please guide me is there any risk associate with me ? Regards,