The apache error log shows
[Wed Oct 28 23:49:30 2015] [error] [client xx.xx.xxx.xxx] ModSecurity: Input filter: Failed to create temporary file: /root/tmp/20151028-234930-VjGXSkAWQiQAA@W7VAsAAAAD-request_body-nKiZdT [hostname "www.xxxx.com"] [uri "/wp-admin/admin.php"] [unique_id "VjGXSkAWQiQAA@W7VAsAAAAD"]
The issue is because the modsecurity has no access on /root/tmp directory.
So while accessing /root/tmp it will show the error “Failed to create temporary file”
The issue can be fixed by adding the following lines on the configuration file of modsecurity.
# vi /usr/local/apache/conf/modsec2.conf
Add these below lines in /usr/local/apache/conf/modsec2.conf
SecUploadDir /tmp SecTmpDir /tmp SecDataDir /tmp SecRequestBodyAccess On
Now you need to restart apache to make the changes effective
service httpd restart
This will fix the issue normally