Description

Detects dangerous usage of JavaScript eval() function in Scala.js applications where untrusted input could be executed. This can lead to arbitrary code execution vulnerabilities when user-controlled data is evaluated as code.

Detection Strategy

• Check if the Scala.js JavaScript interop library (scala.scalajs.js) is imported in the source code

• Look for calls to the 'eval' function in the code

• Verify if the eval function receives data that originates from user input or external sources

• Report a vulnerability when eval is called with untrusted input that could lead to code injection

Vulnerable code example

package controllers

import play.api.mvc._
import scala.scalajs.js

def vulnerable: Action[AnyContent] = Action { request =>
  // VULNERABLE: Directly executing user input via js.eval
  val userCode = request.getQueryString("code").getOrElse("")...

✅ Secure code example

package controllers

import play.api.mvc._
import scala.scalajs.js

def safe: Action[AnyContent] = Action { request =>
  val userCode = request.getQueryString("code").getOrElse("")
  ...