The instructions for adding "AllowEncodedSlashes On" setting are:
Make the following directory. Replace username with the username of the user and domain.tld with the domain.
mkdir -p /etc/apache2/conf.d/userdata/ssl/2_4/CPANELUSERNAME/DOMAIN.TLD/
mkdir -p /etc/apache2/conf.d/userdata/std/2_4/CPANELUSERNAME/DOMAIN.TLD/
Create slashes.conf file
vi /etc/apache2/conf.d/userdata/std/2_4/CPANELUSERNAME/DOMAIN.TLD/slashes.conf
add
AllowEncodedSlashes On
to the file.
Copy the code slashes.conf to SSL folder:
cp/etc/apache2/conf.d/userdata/std/2_4/CPANELUSERNAME/DOMAIN.TLD/slashes.conf
/etc/apache2/conf.d/userdata/ssl/2_4/CPANELUSERNAME/DOMAIN.TLD/
Once this is done, you rebuild the httpd.conf file, so this is included in the webservers configuration:
/usr/local/cpanel/scripts/rebuildhttpdconf
Lastly, restart Apache so the configuration is loaded:
/usr/local/cpanel/scripts/restartsrv_httpd
Debugging ModSecurity
If this is not working, try disabling modsecurity. Rule ID's 930120 and 949110 are hit when implementing the changes.