Language: PHP
Label: vulnerable
CWE: CWE-77 \u2014 Improper Neutralization of Special Elements used in a Command ('Command Injection')
The product constructs all or part of a command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended command when it is sent to a downstream component.

Code:
	public function accessTokenCheck($accessToken){
		$systemPassword = Model('SystemOption')->get('systemPassword');
		if(!$accessToken || strlen($accessToken) > 500) return false;
		
		$pass = substr(md5('kodbox_'.$systemPassword),0,15);
		$sessionSign = Mcrypt::decode($accessToken,$pass);
		if(!$sessionSign || $sessionSign != Session::sign()) return false;
		return true;
	}