XSS in Repetico Android Web Backend

Executive Summary

This is a stored Cross-Site Scripting (XSS) vulnerability in the Repetico Android app version 1.9.7.31. It allows an authenticated user with low privileges to inject arbitrary JavaScript into the question text field of a multiple-choice flashcard. The injected script is stored and executed in the app's web context when the flashcard is viewed.

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Detection Guidance

To detect this XSS vulnerability, inspect flashcard sets for malicious JavaScript in question text fields. Check for unusual payloads like <script> tags or event handlers in stored flashcard content. Use browser developer tools to monitor network requests and responses for suspicious data flows.

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Impact Analysis

The vulnerability can lead to arbitrary JavaScript execution in the app's web context when viewing flashcards. Since flashcard sets can be shared publicly, the impact extends to other users who open these sets, potentially exposing their data or session.

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Compliance Impact

This XSS vulnerability could potentially violate compliance with GDPR and HIPAA by enabling unauthorized JavaScript execution in the app's web context. For GDPR, it may lead to unauthorized data access or manipulation if user data is exposed or altered. For HIPAA, if the app handles protected health information, the vulnerability could allow unauthorized access or disclosure of sensitive data.

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Mitigation Strategies

Apply context-aware output encoding and server-side sanitization to user-supplied flashcard fields. Enforce a restrictive Content Security Policy in the WebView. Avoid opening flashcard sets from untrusted authors until a patch is available.

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