Is financial gain from customers subscribing to a marketing group permissible, given that the subscriber pays to join the group, and no money is taken from the merchant or for the product, but the group may include products whose content has not been fully verified, such as the presence of one book with prohibited content within a displayed set of books, knowing that the group owner does not read all the displayed products?

It is permissible to market products on social media and take a known commission from customers under two conditions: that the products be permissible, in accordance with the Almighty's saying: (And cooperate in righteousness and piety, and do not cooperate in sin and aggression), and that the commission be known in kind and amount.

If the product includes components, a strong presumption that it is permissible is sufficient as long as its origin is permissible and it does not lead to vice, due to the impossibility of certainty. As stated in Sharia, "That which there is no way to know its reality: the ruling therein is based on the predominant opinion."

In summary: There is no harm in being ignorant of the product's components as long as its origin is permissible and its freedom from what is unlawful is strongly presumed.