Temporarily Turn off Modsec filtering
You can temporarily turn off Modsec filtering by adding a code snippet rule to your .htacces file, this can be helpful if you are triggering a number of rules which are false positives or you are unable to get the rules whitelisted whilst you do your development.
Add into .htaccess
<IfModule mod_security.c> SecFilterEngine Off SecFilterScanPOST Off </IfModule>
This should be removed once you have done what you need and the site is subject again to the modsec rules in place.