1) it becomes increasingly more dangerous to dl stuff from the internet and just run it, even its opensource, given normally people don't read all of it. for weird repos I'd recomment to do automated analysis with opus 4.5 or the gpt 5.2 indeed.
2) if we assume adversaries are using LLMs to churn exploits 24/7, which we should absolutely do, perhaps the time where we turn the internet off whenever is not needed, is not far.
You are right: 30 years ago, it was safe to go to vendor XY page and download his latest version and it was more or less waterproof. Today with all these mirror sites, very often better SEO ranking than the original, its quite dangerous: In my former bank we had a colleague who installed a browser add-in that he used for years (at home and in the bank); then he got a new notebook, fresh browser, he installed the same extension - but from a different source than the original vendor: unfortunately, this version contained malware and a big transaction was caught by compliance in the very last second, because he wasnt aware of data leakage.
You _are_ joking, right? I distinctly remember all sorts of dubious freewarez sites with slightly modified installers. 1997-2000 era. And anti-virus was a thing in MS-DOS even.
but, you are old enough - so mean pages like fosi.da.ru back then? ;-)