What is the ruling on contributing to or speculating in stocks, knowing that some scholars have prohibited shares of all companies?

Companies are classified into three types: permissible/pure companies (whose core business is permissible and adheres to Sharia), forbidden companies (whose core business is forbidden), and mixed companies (whose core business is permissible but deals with some forbidden matters). It is permissible to invest in permissible/pure companies. As for forbidden companies, it is not permissible to invest in them or promote them. Contemporary scholars have differed on the ruling regarding mixed companies, but the preponderant opinion is that it is forbidden to invest in them or promote them; this is because the shareholder is a partner in the forbidden dealings of the company. For this reason, fatwas have been issued by jurisprudential councils prohibiting investment in mixed companies.