I guess to fix this, we would need to inject the xredirect parameter in javascript at the moment the link is clicked. Another possibility is to disable that feature when action==export (since, whatever the export, it probably does not make much sense to redirect to an export after a login).

For me it feels like there's two different problems. On the first place, the html export should just never provide a login link: you're accessing a static HTML version of the wiki, you probably don't want those links / button to be available at all?

Now for the redirect part of the login link, ideally in the future the login should be handled mostly by some JS and not redirect to another page at all.