If you are facing any internal server error in your website after enabling mod security than most possibly that there is two issue ONE OF THEM IS RESPONSE BODY TOO LARGE SOLUATION.For
Example :-
go in Centos Web Panel CWP:-
https://your Ip :2031/index.php?module=mod_security
and see........................
[Mon Jan 18 18:46:07 2016] [error] [client 192.168.1.1] ModSecurity: Output filter: Response body too large (over limit of 524288, total not specified). [hostname "example.com"] [uri "/website page path/post.php"] [unique_id "Vp15PX8AAAEAADPPMLAAAAAC"]
Than there is a
Soluation for Centos Web Panel CWP:-
open
https://your IP :2031/index.php?module=file_editor&file=/usr/local/apache/conf.d/mod_security.conf
or /usr/local/apache/conf.d/mod_security.conf
YOU ARE MOST PRPROBABLY SEE THE FOLLOWING CODE:-LoadFile /usr/lib/libxml2.so
LoadFile /usr/lib/liblua-5.1.so
LoadModule security2_module modules/mod_security2.so
<IfModule mod_security2.c>
SecPcreMatchLimit 1000000
SecPcreMatchLimitRecursion 1000000
SecDataDir logs/tmp
</IfModule>
ServerName *
AddDefaultCharset UTF-8
<IfModule mod_security2.c>
Include /usr/local/apache/modsecurity-crs/modsecurity_crs_10_config.conf
Include /usr/local/apache/modsecurity-crs/base_rules/*.conf
SecRuleEngine On
SecRequestBodyAccess On
SecResponseBodyAccess On
Include /usr/local/apache/conf/mod_sec_disabled_rules.conf
</IfModule>
IN THIS CODE .. SEE THE LAST 3RD LAST LINES AFTER SecRequestBodyAccess On
SecResponseBodyAccess On
PUT THESE LINESSecResponseBodyLimit 546870912
SecRequestBodyInMemoryLimit 546870912
SAVE AND NOW IN RESTART APACHE OR IN YOUR PUTTY TERMINAL RUN THIS COMMNAD
service httpd restart