Squid sslbump works with closed connection warning

Question

I am using squid 3.5 with its sslbump function to filter https traffic. I created my private keys and cert files using openssl. However, the browser received a warning message when I opened https sites that the certificate was issued by an unknown authority. I created ssl certificates with comodo, but I still have the same warning.

Is there any way to remove this warning?

# Squid normally listens to port 3128
http_port 3128 ssl-bump cert=/var/tmp/example.com.cert key=/var/tmp/example.com.private

# Squid listen Port
cert=/var/tmp/example.com.cert
# SSL Bump Config
always_direct allow all
ssl_bump server-first all

url_rewrite_program /usr/bin/sh /var/tmp/middle_squid_wrapper.sh start -C /var/tmp/middle_squid_config.rb

# required to fix HTTPS sites (if SslBump is enabled)
acl fix_ssl_rewrite method GET
acl fix_ssl_rewrite method POST
url_rewrite_access allow fix_ssl_rewrite
url_rewrite_access deny all