According to Steam's policy: "all community market transactions are final and cannot be reversed or refunded", I understand that.

But if someone hacks (by malware or a phishing email getting the login credentials) your Steam account, disables notifications and buys overpriced useless items with your money... It's hard to believe that Steam does nothing to prevent this kind of theft.

However, there are many possible solutions to reduce the risk or even avoid the above:
1. do not allow low level users to trade. Who have no games, hours played or it is clearly a fake account: may not be allowed to sell
2. send an email with a link or code to approve the transaction
3. profile settings changes should also be protected with at least a confirmation email

Steam has its share of the theft. According to them, they cannot recover money from the seller's wallet. And what about the cut they made on the transaction? Did anyone get a refund?

And most importantly, why aren't they doing anything about it?

The idea is to let Steam know about the need for security changes in the community market.

Please sign the petition, thank You!