Rule Definition
Using 'Throwable.printStackTrace()' usually means that it is used to log the stack of errors, which has the risk of filling up the stdout or the log file. Moreover, it is accessible to end-user which is bad for security and user-experience. It is recommended to use a Logger instead.

Remediation
1. Loggers should be used instead to print Throwables, as they have many advantages:Users are able to easily retrieve the logs. The format of log messages is uniform and allows users to browse the logs easily. 2. Define a specific stream where the stack trace is to be printed.

Violation Code Sample

fun main(args: Array<String>){
    try {
        test()
    } catch (e: UnsupportedOperationException) {
        e.printStackTrace()
    }
}

Fixed Code Sample

fun main(args: Array<String>){
    try {
        test()
    } catch (e: UnsupportedOperationException) {
        LOGGER.log("context",e) //Violation Fixed: Logger is used
    }
}

________________________________________________

fun main(args: Array<String>){
    try {
        test()
    } catch (e: UnsupportedOperationException) {
        e.printStackTrace(stream: PrintStream) //Violation fixed: A specific stream is defined to print the stack trace
    }
}

http://cwe.mitre.org/data/definitions/489.html OWASP Top 10 2017 Category A3 - Sensitive Data Exposure