Nginx possibly removing dot (".") from URL path before forwardslash

I have defined a reverse proxy like this:

    server {
        listen       443 ssl;
        server_name  testing.com;
        ssl_certificate      "C:/nginx/testing.crt";
        ssl_certificate_key  "C:/nginx/testing.key";
        location / {
            proxy_pass  "http://127.0.0.1:8888/";
        }
    }

The reverse proxy works as intended. Now that we got that out of the way:

I have a case where i need to pass parameters in the URL and some of the parameters sometimes end with a dot (.) like this "https://testing.com/param1./param2/param3/param4."
But for some reason the URL that is received at the server looks like this "127.0.0.1:8888/param1/param2/param3/param4"

If i call the server directly like this "127.0.0.1:8888/param1./param2/param3/param4.", the parameters are correct. My guess is that nginx modifies the URL. Maybe the issues lies somewhere else...

I am on Windows 10. The server is a Go (golang) server that uses only built in libraries. I have setup self signed certificates and edited my hosts file (never had issues with those).

ALSO - my friend who is also working on this project has no issues even tho we have identical nginx setups, but the only difference is that he is on Linux.

You have run into the features implemented in nginx versions 1.3.1 and 0.8.6 for Windows:

Changes with nginx 1.3.1                                         05 Jun 2012

    *) Security: now nginx/Windows ignores trailing dot in URI path
       component, and does not allow URIs with ":$" in it.
       Thanks to Vladimir Kochetkov, Positive Research Center.

Changes with nginx 0.8.6                                         20 Jul 2009

    *) Bugfix: now nginx/Windows ignores trailing dots in URI.
       Thanks to Hugo Leisink.

(http://nginx.org/en/CHANGES-1.24)

In fact, nginx also ignores trailing spaces in paths too, only on Windows:

Changes with nginx 0.8.33                                        01 Feb 2010

    *) Security: now nginx/Windows ignores trailing spaces in URI.
       Thanks to Dan Crowley, Core Security Technologies.

    *) Security: now nginx/Windows ignores short files names.
       Thanks to Dan Crowley, Core Security Technologies.

The period related changes were introduced in commits f83598a35981197ac113b9c898bdb972aa8366da (in 1.3.1) and 2376d6082ab407a68619bfeb753c825e30617e2d (in 0.8.6).

I found this out while debugging a similar issue with nginx 1.20.1, where on Windows the reverse proxied requests would drop all periods from the end of the request path. Looking at the URL parsing source code at the time of writing this response, it doesn't look like this feature is configurable.

It's possible to slightly work around this by using $request_uri with the proxy_pass like so:

proxy_pass http://127.0.0.1:8888$request_uri;

This sends the unprocessed URI path to the upstream. Of course this isn't affected by location rules since it's the original path, so you may end up with a different path than you need. Additionally, if you are using the path to access/serve files, take note of the security issues that this period/space normalisation is trying to protect you from.