To conduct a security assessment of the iOS application, you need to follow some standard criteria from industry. Open Web Application Security Project (OWASP) Top 10 Mobile Risks is the list of vulnerabilities that are usually found in iOS applications.
You can always find latest top ten list for mobile at https://www.owasp.org/index.php/Projects/OWASP_Mobile_Security_Project_-_Top_Ten_Mobile_Risks.
The major difference between the latest OWASP Top 10 Mobile Risks and its earlier versions is the introduction of a new vulnerability in the list, that is, the lack of binary protection, which is the replacement of sensitive information disclosure.
The latest OWASP Top 10 Mobile Risks, Year 2014 list covers the following vulnerabilities: ...