Upgrading my instance to 0.18.0 has caused a lot of problems. One major issue is the main web UI won't even load (returns a blank page with just text Server error), unless you manually remove the site's image icon via a SQL query in the Postgres database. So, upgrade to 0.18.0 at your own risk.
Also, this is not intended as a criticism to anyone. Just a warning that 0.18.0 is a bit unstable and waiting for 0.18.1+ is a safer option for the larger hosted communities (my opinion).
Devs will be addressing the submitted captcha fix after the weekend (they said so on GitHub). So I hope 0.18.1 drops early next week. They wanted 0.18 released before 3rd party apps die, so I presume having the largest instance holding back will give them a reason to push it before the end of the week.