Will offer my way of fixing.. probably something went wrong in the themes, aside from css, probably version mismatches with the core nodebb version your using. The below will revert to working vanilla and lavender theme versions that match w/ your core nodebb install version. (probably need to stick with whatever theme versions it reinstalls, because I've always had problems w/ updating themes, I don't upgrade them anymore) Stick with what came with the nodebb install originally. This will revert back to originals:
It's a bit off-topic but still related to default settings for external links. I haven't tested the acp of 0.7.0 yet and I was wondering if there was something like a whitelist for external links? Then if someone click on an external link we can activate the warning page "you are leaving the forum", but if it's a sub domain, a root domain or a trusted url (youtube) for example we don't show this page.