What is the ruling on commission earned from selling products discounted due to non-Muslim holidays, given that the seller's website does not promote these holidays, but rather directs buyers to company websites that may offer these promotions?

If your dealings with foreign companies are in permissible matters, then there is no harm in benefiting from discounts and commissions, even if it coincides with their holiday. The principle is the permissibility of buying, and its occurrence during their holiday does not cause harm. Benefiting from discounts does not constitute aiding in a sin, unless there is participation in the manifestations of their celebrations. Some scholars have explicitly stated the permissibility of buying from the markets of the polytheists that they establish during their holidays. Sheikh al-Islam Ibn Taymiyyah says: A Muslim should not sell anything that aids in their imitation during the Eid. As for trading with them for what they use for their Eid, or attending their Eids for purchasing, Imam Ahmad was asked about the Eid markets that Muslims frequent for shopping, and he permitted that, provided they do not enter their churches.