How do i hacker hack a whmcs installation?

[Webbstart]

How do a hacker hack a whmcs installation and how do i prevent it?

[Kian]

Backdoors. From my experience the backdoor usually comes from another CMS installed on the same hosting package. Long story short by cracking Wordpress they get WHMCS.

[Webbstart]

Whmcs is the only software installed on my hosting package. How do i secure Whmcs?

[Kian]

https://docs.whmcs.com/Further_Security_Steps

 

[Remitur]

A couple of tricks to add to what suggested by WHMCS:

• enable and force 2FA for admin access 
• keep your backup(s) on a different system
• do not use "strange" (nulled...) themes and add-on
• protect your phpmyadmin access  

[WHMCS Lawrence]

Generally the most common source of intrusion can be traced to third party PHP software that has been installed alongside WHMCS, such as Joomla!, WordPress, or many others, that have publicly known exploits or weaknesses at the time. Following any compromise, a complete server or account audit is usually warranted, including searching for any files you do not recognize, in particular any shell scripts or uploaders that many hackers leave in place to allow future compromises. During a security audit, any scripts or third party software should be updated to the latest versions, including any security patches. 

Once this has been completed, our recommendation would be to delete all files on your WHMCS hosting account except for the WHMCS configuration.php file (including the files in other directories as well) in case the hackers have left any malicious files behind to be able to return later. This will allow you to begin with a "clean slate" by uploading a fresh set of WHMCS files, while using your existing database. 

Protecting your WHMCS installation is all about your server security. WHMCS can only ever be as secure as the server it is hosted on, so you need to ensure you have permissions on the server set appropriately so other shared users can't read or access your files, you also need to ensure you do not install any third party scripts which frequently have security issues in the same hosting account as WHMCS, and if possible you should consider moving WHMCS to an isolated VPS or dedicated environment for higher security.

Please also view http://docs.whmcs.com/Further_Security_Steps for information on keeping your WHMCS Installation secure.