If I press Ctrl+S on a website and download it to my desktop, then open it in Firefox, can it access my desktop files or install malware?

I downloaded a not-so-reputable website to my desktop as a way to grab the images on the site. I tried opening the HTML and then I remembered hearing that opening a local file in a browser is different from opening a website. Something about http:// and file:/// allowing different levels of access to my computer. Unsure if I should just re-install windows just to be safe.

I tried scanning the website folder with microsoft defender and it said that no threats were found but IDK how foolproof microsoft defender is.