After upgrading to 9.13.11 we saw that the prices weren't retrieved in cart anymore using the price provider, while in the product list or product detail everything was fine. After debugging we saw that for the price provider call in the cart context, Dynamicweb passes an empty user to the price provider:
PriceRaw FindPrice(Product product, double quantity, string variantId, International.Currency currency, string unitId, User user)
The user argument is null, but only when it is in a cart context (like adding to cart), otherwise everything it's fine.
We patched it by using in the price provider the following line at the start of the method:
user = user ?? User.GetCurrentExtranetUser();
Please fix this as a lot of existing solutions will suffer from this bug.