Comprehensive Security Audit and Penetration Testing

I need a thorough security audit and penetration testing for our mobile app.

Requirements:
- Identify security weaknesses, backdoors, or exploitable vulnerabilities.
- Perform grey box penetration testing.
- Provide a detailed report of findings with risk ratings.
- Recommend and assist in implementing security fixes and best practices.

Ideal Skills and Experience:
- Expertise in mobile app security.
- Experience with grey box penetration testing.
- Strong analytical skills for risk assessment.
- Familiarity with security best practices and remediation.