Is social security permissible if its fund is invested in accordance with Islamic Sharia and supports members in cases of death, disability, or unemployment? Is the return from this fund permissible for the member, and does this fall under the principle of social solidarity?

Dealing with what is called "social security" is permissible according to certain regulations. Investing this money in ways that conform to Sharia (definition) is permissible for its growth, but the profit is not distributed to the members, because the intention is cooperation and assistance, not profit generation. Its ruling is like the ruling of the principal money; it is distributed according to need.