Absolutely.

Wikipedia isn’t wholly unprotected from vandalism and other such attacks, they always keep a post history, users without an account are logged, admins can lock pages or ban people, and I dunno all the details but some things can cause an automatic rollback, but yeah.

There’s nothing stopping me from messing with styles, content, inserting external links to things. If I do it in a way that’s against the rules, there’s also nothing stopping someone from reverting all my changes in a couple of clicks and banning me or my IP. If someone was truly malicious and used a VPN to dodge bans, that’ll get a page locked from everyone and make edits need to be approved, which is much more common for political pages.

But yeah, Wikipedia is open, and that means open.