Hello,
We’re pushing today a pretty big change to how we handle apps that aren’t on a custom domain yet. They use to be on a domain https://bubble.io/site/forum_app/version-test/ and we’re moving them to https://forum_app.bubbleapps.io/version-test/. Doing so helps us solve a few issues, including security aspects, handling cookies (so that the forum won’t break any more if you have too many cookies), etc. It’s also a bit prettier, but that won’t matter much since as soon as apps are launched they are on a custom domain.
When you’ll hit ‘PREVIEW’ in the editor, you’ll be taken to the new URL. We still support for the former system, but we’ll deprecate this over the next week or two and will redirect automatically pages to the new domain.
If you have your link in some places (for instance Stripe connect, Oauth, etc.), please change that soon, so that we can smoothly deprecate the old system.