seblg on "$wpdb->update vs $wpdb->query->prepare"

Hi,

My plugin (http://ostenta.fr/yawpp/index_en.html) has been temporarily withdrawn due to a security issue. (SQL injection)

I tried to fix it but I recieved a new mail because I wasn't using prepare() to update rows in the DB.

Actualy, I'm using update() function.

What is the best way to update a rows?