Reflected XSS in Appium via Unescaped User Input

Compliance Impact

The vulnerability allows reflected cross-site scripting (XSS) that can lead to arbitrary JavaScript execution on the server origin, potentially enabling attackers to interact with the WebDriver REST API and plugin endpoints. This could result in unauthorized data modification, impacting data integrity.

Such unauthorized data modification and potential exposure of sensitive data could affect compliance with standards and regulations like GDPR and HIPAA, which require protection of data integrity and confidentiality.

However, these vulnerable routes should not be accessible in production environments, and the issue is fixed in version 10.7.0, mitigating the risk when updated.

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Impact Analysis

The vulnerability can lead to reflected cross-site scripting attacks, which allow attackers to execute arbitrary JavaScript code in the context of the server origin. This can result in unauthorized actions, data theft, session hijacking, or other malicious activities affecting users interacting with the vulnerable Appium server.

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Mitigation Strategies

To mitigate this vulnerability, you should upgrade Appium to version 10.7.0 or later, where the issue has been fixed.

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Executive Summary

This vulnerability exists in Appium versions prior to 10.7.0, where the base-driver unconditionally mounts certain test routes (/test/guinea-pig, /test/guinea-pig-scrollable, and /test/guinea-pig-app-banner). The compileLodashTemplate function reflects the throwError query parameter, comments POST field, and User-Agent request header into HTML without proper escaping. This allows an attacker to perform reflected cross-site scripting (XSS) attacks, enabling arbitrary JavaScript execution on the server origin.

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Detection Guidance

This vulnerability can be detected by checking if the Appium server is exposing the debug/test routes that are vulnerable, specifically /test/guinea-pig, /test/guinea-pig-scrollable, and /test/guinea-pig-app-banner.

You can attempt to send crafted HTTP requests to these routes on the Appium server and observe if the response reflects user-controlled input such as the throwError query parameter, comments POST field, or User-Agent header without proper escaping.

Example commands using curl to test for the vulnerability include:

• curl -v "http://<appium-server>:<port>/test/guinea-pig?throwError=<script>alert(1)</script>"
• curl -v -X POST -H "User-Agent: <script>alert(1)</script>" -d "comments=<script>alert(1)</script>" "http://<appium-server>:<port>/test/guinea-pig-app-banner"

If the response contains the injected script tags unescaped, the server is vulnerable.

Note that these routes should not be accessible in production environments, so their presence and behavior can indicate vulnerability.

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