Possible reason for NGINX 499 error codes

Question

I\'m getting a lot of 499 NGINX error codes. I see that this is a client side issue. It is not a problem with NGINX or my uWSGI stack. I note the correlation in uWSGI log

Answer 1

Once I got 499 "Request has been forbidden by antivirus" as an AJAX http response (false positive by Kaspersky Internet Security with light heuristic analysis, deep heuristic analysis knew correctly there was nothing wrong).