OS command Injection vulnerabity

"OS=Operating System" command injection vulnerability is a high impact vulnerability for server/website.  If any website has OS command injection vulnerability Then a malicious hacker can compromise the website or even the server operating system. If a hacker can detect the vulnerability then he can run any Operating system command. For example, If i run the command "rm -r /var/www"  on my computer then it is going remove "www" but what if i run this command on my victim's computer ?

How we detect this vulnerability:
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