WARNING: Free Steam GC from stAEmcommunity.com

Pretty smart. Most people won't look that closely at a url.
Have you let your friend know about this user?

Just the usual scam attempt
Report your "friend" as they probably aren't even aware their account has been hijacked.
Edit: Messaging them will just mean talking to the hijacker.

That kind of a message is very suspicious. Why would someone send me a free $50 out of nowhere?

I got other message asking me to vote their workshop items, with weird steam link. Never trust suspicious links.

I received a message like this today

I got it too, but the url was steanmcoommunity.com i believe. I asked whether they were hacked and they said yes sometime later.

I haven't seen this, but good luck to your friend in getting their stolen account back!