alt Hacker NewsPro tip: I’ve seen plenty of dedicated extensions that could have just been simple snippet equivalents in Tampermonkey - an extension that lets you run JS limited to wildcarded websites.
I've used it to inject download links on sites, autoclose modals, etc. You can either write them yourself, or review other people before installing them.
It’s not a perfect solution, but at least it reduces the surface area to a single extension.
FYI: Just set Script Updates to Never.