Language: PHP
Label: vulnerable
CWE: CWE-74 \u2014 Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
The product constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is parsed or interpreted when it is sent to a downstream component.

Code:
    public function checkFilesExist(&$input)
    {

        if (isset($input['tls_certfile'])) {
            $file = realpath($input['tls_certfile']);
            if (!file_exists($file)) {
                Session::addMessageAfterRedirect(
                    __('TLS certificate path is incorrect'),
                    false,
                    ERROR
                );
                return false;
            }
        }

        if (isset($input['tls_keyfile'])) {
            $file = realpath($input['tls_keyfile']);
            if (!file_exists($file)) {
                Session::addMessageAfterRedirect(
                    __('TLS key file path is incorrect'),
                    false,
                    ERROR
                );
                return false;
            }
        }
    }