possible security issues on shared hosting.

[desiguru]

What are the possible risks if you run cpanel with gd library?

Also what should I do if I wanted to make a secure host for all of my clients?

[cPanelDon]

Moderator Note: I've relocated this forums thread into the cPanel and WHM Security area so the topic can receive more relevant discussion applicable to the questions involved.

Regarding GD; as with any additional software, if there is a vulnerability in the extra software then that may incur more risk for the system it's installed on.

Regarding security suggestions, I recommend reviewing the following documentation resource to help learn about the available security features and functions in cPanel/WHM:
WhmSecurity < AllDocumentation/WHMDocs < TWiki

Here are two additional, related areas of documentation that include details about general settings and configurations that can be tweaked, some of which have security implications:
TweakSettings < AllDocumentation/WHMDocs < TWiki
ServiceConfig < AllDocumentation/WHMDocs < TWiki