wp-login.php not being parsed upon submit

So, I just installed wordpress on a brand new VPS setup (running nginx/php-fpm). Everything was fine till I tried to login with another browser due to an issue with chromium. I can access wp-login.php fine, but once I submit the login form, firefox just shows a download prompt (which downloads an empty file). I’ve checked my nginx and php-fpm error logs and there’s no mention of any errors relating to wp-login.php.

I’d really appreciate some help with this as I have no idea what the problem may be.