No, instead you're just reading all files on the filesystem, including the browser's cookie store or whatever. The data you are, or can be, handling is just as, if not more, sensitive since it's literally a superset of what the browser has access to.
> The lack of sandboxing in desktop applications is bad
Some sandboxing would be nice, but the Google/Apple approach of needing to beg the vendor for every little permission isn't the way to go, either. I'd rather have software that can actually do things as opposed to only having useless sandboxed "apps".