cPanel::3rdparty::ModuleInstaller is a perl module hosted on CPAN. Basically this module allows Host Manager backend to be installed as a CGI script in
/usr/local/cpanel/whostmgr/docroot/cgi/.
All calls to this module are secure and installing the backend is the only thing that this module do.

To install the module you should have root access to server, login as root and run:

#cpan cPanel::3rdparty::ModuleInstaller

You can also use WHM (Web Host Manager) of cPanel to install it as a Perl Module. Login to WHM as root, in software section click on 'Install a Perl Module', type 'cPanel::3rdparty::ModuleInstaller' in the box bellow the Install a Perl Module and click install.

When module installed, login to the server using Host Manager app on iPhone or iPad. App will automatically install or update the backend engine (aka HM Backend).

HM Backend is a CGI script that will be installed in /usr/local/cpanel/whostmgr/docroot/cgi/ folder. It helps the Host Manager app to get and set data on the server more efficiently. cPanel already has an API for WHM, Why we need this module? Lots of functions does not work properly or produce different results than what you get in WHM. Therefore we had to rewrite them using Cpanel perl modules. Here are a few examples (cPanel version 11.30):

• When you want to get list of SSL Hosts, cPanel API gives you all domains including server host name! while in WHM you are getting the correct list.
• If you give a reseller permission to terminate his own accounts privilege will be there, but cPanel API does not allow you to use killacct function.
• There is no function in cPanel API to get current DNS resolvers
• There is no function in cPanel API to delete a reseller ACL

Additionally some operations may take a while to get completed. For instance if you want to terminate a reseller account with all his 400 domains you might endup loosing your battery. In this case this module accepts the command and run it in background. Then send you a push notification when task completed.

Just take a look at WHM API in cPanel web site and compare it to what you can do in web interface of WHM.

HM Backend is open source and you can examine the functionality for security concerns, location of the CGI file is:

/usr/local/cpanel/whostmgr/docroot/cgi/hm_iphone_wrap_X.X.cgi

where X.X is the current major version of the backend.