Overview

When an app uses evaluateJavaScript(_:completionHandler:)) to read data from the DOM (for example, to extract form field values, account details, or page structure), the script executes in the .page world. In this world, the JavaScript prototype chain is shared with page scripts. A malicious or compromised page can override built-in functions such as document.querySelector or Element.prototype.getAttribute before the inspection code runs, causing it to return attacker-controlled values instead of the real DOM content.

The content-world-aware variant evaluateJavaScript(_:in:in:completionHandler:)) runs the script in an isolated world with an independent prototype chain that page JavaScript cannot modify.

This test checks whether the app uses the legacy evaluateJavaScript:completionHandler: selector when reading DOM data in security-relevant contexts.

Steps

  1. Use MASTG-TECH-0058 to extract the relevant binaries from app package.
  2. Use MASTG-TECH-0066 to look for the relevant APIs in the app binaries.

Observation

The output should contain a list of locations where evaluateJavaScript:completionHandler: is called, along with the enclosing function symbols.

Evaluation

The test case fails if evaluateJavaScript:completionHandler: is used to read DOM content in a security-relevant context.

Further Validation Required:

Inspect each reported call site using MASTG-TECH-0076 to confirm whether the evaluated JavaScript string reads data from the DOM (for example via document.querySelector, document.getElementById, getAttribute, .value, .textContent, or .innerHTML) and whether that data is security-relevant, such as account details, credentials, or authentication tokens.

Also confirm that the call uses the legacy evaluateJavaScript:completionHandler: selector rather than the content-world-aware evaluateJavaScript:inFrame:inContentWorld:completionHandler: variant. Only the legacy selector runs in the .page world, where page JavaScript can override built-in functions (such as document.querySelector) and return attacker-controlled values; reads performed in an isolated content world are not affected.

Linked Issues

Issuelinks
is related to MASTG-BEST-0061 Use WKContentWorld Isolation for DOM Inspection Scripts (iOS)