Client Side Vulnerabilities / Web Messaging

Description

Web Messaging is a type of Client Side Vulnerability occurring in Web and API applications. It is a class of vulnerability that is defined in the Common Weakness Enumeration (CWE) directory as CWE-918 (Ref 1). This type of vulnerability occurs when an application does not properly validate and sanitize input from users and ends up allowing malicious code execution. The OWASP Testing Guide (Ref 2) provides a more detailed description of the vulnerability and how it can be exploited.

Risk

Web Messaging vulnerability has a high risk as it can lead to the compromise of sensitive user data, denial of service attacks, and other malicious activities. Malicious actors can inject code that can be executed on the client-side in order to perform malicious activities, such as changing the appearance of webpages and stealing user information. This increases the risk of data breaches and other attacks.

Solution

The best way to mitigate this type of vulnerability is to ensure that user input is properly validated and sanitized. Input validation should be done on the server-side, while output validation should be done on the client-side to ensure that malicious code is not executed. Additionally, the application should be regularly tested for any potential vulnerabilities.

Example

An example of a Web Messaging vulnerability is CVE-2017-9552 (Ref 3). This vulnerability occurs when a web application does not properly validate user input and ends up allowing malicious code to be executed on the client-side. The code snippet provided in the CVE is as follows:

<script>
  var payload = "alert(1)";
  window.parent.postMessage(payload, "*");
</script>

This code snippet allows a malicious actor to inject code that can be executed on the client-side without any user intervention.