I recently upgrading from a fully working version of dynmap 2.3 (I think) with Spigot 1.11.2 to dynmap v3.0-beta-10-257 with Spigot 1.15.2. I have my web server bound to localhost only and I use nginx as a reverse proxy.

After the update, dynmap loaded correctly but when accessed from nginx it always redirects users to localhost, which obviously doesn't work:

❯ curl -v <redacted>
*   Trying <redacted>...
* TCP_NODELAY set
* Connected to <redacted> (<redacted>) port 80 (#0)
> GET / HTTP/1.1
> Host: <redacted>
> User-Agent: curl/7.64.1
> Accept: */*
>
< HTTP/1.1 302 Found
< Server: nginx/1.17.10 (Ubuntu)
< Date: Sat, 23 May 2020 21:50:04 GMT
< Content-Length: 0
< Connection: keep-alive
< Location: http://localhost:8123/index.html
<
* Connection #0 to host <redacted> left intact
* Closing connection 0

There are no hosting services involved here, I'm managing my own web server and DNS configuration manually.

I haven't changed any config whatsoever. Was there any change in behavior from older versions of dynmap to v3.0-beta-10-257 that could have caused this?

This seems to be fixed in v3.0-RC3-331.