1. Vulnerability Description

• If Java Conversion does not occur explicitly, unexpected errors can occur.

2. Vulnerability Countermeasure

• Use JavaConverters to explicitly enable Java Conversion, and you must use CollectionConverters after Scala 2.13.

3. Example Code

• Vulnerable code

import scala.collection.JavaConversions._
object Test {
   val jul = new java.util.ArrayList[String]
   val jum = new java.util.HashMap[String,String]
   val a = jul.exists(_ == "sammy")
   val b = jum.toSeq
}

• Safe code

import scala.jdk.CollectionConverters._
object Test {
    val s = collection.mutable.Set("one")
    val js = s.asJava
    js.add("two")