GET /favicon.ico request reports wrong UA

[kli0rf]

I'm spoofing (the whitelist mode) UA for facebook only (i'm pretty sure everybody know the reason:), and yes, it works as expected. However, there's a little bug with them other sites. I'm using firefox 60.9.0esr. That's what nginx's log show:

rem.ote.add.ress - - [16/Oct/2020:00:29:18 +0300] "GET /stuff HTTP/1.1" 301 169 "-" "Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:60.0) Gecko/20100101 Firefox/60.0"
rem.ote.add.ress - - [16/Oct/2020:00:29:18 +0300] "GET /stuff/ HTTP/1.1" 200 1761 "-" "Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:60.0) Gecko/20100101 Firefox/60.0"
rem.ote.add.ress - - [16/Oct/2020:00:29:18 +0300] "GET /favicon.ico HTTP/1.1" 404 1481 "-" "Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:54.0) Gecko/20100101 Firefox/54.0"

First line is ok, the UA is correct, i'm being redirected from http to https. Second line's ok, i got what i wanted. Third line is the GET request for favicon, and this is my spoofed UA which should only be reported to facebook.