We need to install all security patches that required for community edition [ 1.9.0 ]
In this link https://www.magentocommerce.com/download
I found that the following security patches are necessary:
SUPEE-6482, SUPEE-6237 ,SUPEE-5994 , SUPEE-5344,SUPEE-4829, SUPEE-1533 , SUPEE-4291/4334
which security do we need?