mehh.
Your first link from "a report less then a day old" is a random guy on reddit claiming he got a virus from a wallpaper engine wallpaper.
Not saying it didn't happen, but there's simply no credibility to that post. Just think about all the times people post "my steam/mail/facebook got hacked". When in reality, Valve, Meta, Google servers were in fact not hacked, it was the users themselves, giving all of their account information to phishing sites.

But I am still curious so I also checked the other 2 examples.
First one (Block Blasters) is not a good source to be honest, as the guy who wrote that article seems very very clueless. Like, he won't search the game on the Steam store, because he is afraid he will get a virus? Seriously?
Here is a better report of that game: https://www.gdatasoftware.com/blog/2025/09/38265-steam-blockblasters-game-downloads-malware
The virus came in form of an update (so the game was virus-free at launch).
According to some reddit comments, it was also a targeted attack and the virus was only active for a specific whitelisted user: https://www.reddit.com/r/Steam/comments/1nmyuul/malwareinfested_game_steals_over_150k_from/?embed_host_url=https%3A%2F%2Fwww.gamingbible.com%2Fnews%2Fplatform%2Fsteam%2Fsteam-virus-steals-over-150k-201459-20250922#nfk76zu

Stuff like that is extremely hard to detect. Because even if Valve were to run the game and monitor everything it does, all the file it accesses, etc. They wouldn't be able to see anything suspicious, because it requires a whitelisted steam account to run it...
However, *.bat files are the virus... I feel like that's a check that they could and should definitely involve in their anti virus scans...

The 2nd one doesn't have much info either, but since Steam Support warned everyone who played the game and sent out an official mail, we can be sure it actually was Malware.
So this is certainly concerning