Create a simple C++ application that will exhibit concurrency concepts. Your application should create two threads that will act as counters. One thread should count up to 20. Once thread one reaches 20, then a second thread should be used to count down to 0. For your created code, provide a detailed analysis of appropriate concepts that could impact your application. Specifically, address:

• Performance issues with concurrency
• Vulnerabilities exhibited with use of strings
• Security of the data types exhibited.