CVE-2025-63842 Overview
CVE-2025-63842 is a Cross-Site Scripting (XSS) vulnerability in the web backend of the Repetico app version 1.9.7.31 for Android. A remote authenticated user can inject arbitrary JavaScript through the multiple-choice question text field. The injected script executes in the application context when other users render the affected content. The flaw is classified under CWE-79: Improper Neutralization of Input During Web Page Generation.
Critical Impact
Authenticated attackers can execute arbitrary JavaScript in the context of other users' sessions, enabling session data theft, UI manipulation, and abuse of application functionality on behalf of the victim.
Affected Products
- Repetico app for Android, version 1.9.7.31
- Web backend components rendering multiple-choice question content
- User sessions viewing attacker-authored questions
Discovery Timeline
- 2026-09-14 - CVE-2025-63842 published to NVD
- 2026-09-14 - Last updated in NVD database
Technical Details for CVE-2025-63842
Vulnerability Analysis
The vulnerability resides in how the Repetico web backend processes user-supplied input for multiple-choice question text. The application fails to neutralize HTML and JavaScript metacharacters before storing and rendering the field. When another authenticated user loads a question containing malicious markup, the browser parses and executes the payload within the application origin.
Because the flaw requires authentication and user interaction, exploitation depends on victims viewing attacker-controlled content. The scope change indicated by the CVSS vector reflects that injected script can affect resources beyond the vulnerable component itself, including cookies, tokens, and DOM state.
Root Cause
The root cause is missing output encoding on the multiple-choice question text field. User input flows from storage into rendered HTML without contextual escaping such as HTML entity encoding or a Content Security Policy sandbox. Any authenticated account with permission to create or edit questions can persist a script payload.
Attack Vector
An attacker authenticates to the Repetico platform and creates a multiple-choice question containing a crafted payload in the question text field. The payload persists in the backend. When a victim loads the question in a browser or the Android app's web view, the script executes with the victim's session privileges. Refer to the CVE-2025-63842 technical write-up on GitHub for reproduction details.
No verified public exploit code is included here. See the linked advisory for demonstrator payloads.
Detection Methods for CVE-2025-63842
Indicators of Compromise
- Multiple-choice question records containing <script>, onerror=, onload=, or javascript: substrings in the question text field.
- Unexpected outbound requests from user browsers to attacker-controlled domains shortly after loading Repetico content.
- New or modified question entries authored by low-reputation or recently created accounts.
Detection Strategies
- Query the backend datastore for question text fields containing HTML tags or JavaScript event handlers.
- Enable and monitor Content Security Policy (CSP) violation reports for inline script and unsafe-eval events on Repetico pages.
- Correlate web access logs to identify sessions rendering questions immediately followed by anomalous API calls under the same session token.
Monitoring Recommendations
- Log all create and update operations on question objects with the authoring account and full payload.
- Alert on session cookies or bearer tokens being transmitted to domains outside the Repetico origin.
- Track authenticated user accounts that generate a disproportionate number of question edits within short timeframes.
How to Mitigate CVE-2025-63842
Immediate Actions Required
- Restrict question authoring privileges to trusted accounts until a vendor patch is verified.
- Audit stored questions for HTML or JavaScript content and quarantine suspicious records.
- Rotate session tokens for any users that rendered attacker-authored content.
Patch Information
No vendor advisory or patched version was listed in the NVD entry at time of publication. Monitor the Repetico vendor channels and NVD record for CVE-2025-63842 for a fixed release beyond 1.9.7.31. Apply the vendor update as soon as it becomes available.
Workarounds
- Enforce a strict Content Security Policy that disallows unsafe-inline and unsafe-eval for the web backend.
- Apply server-side HTML entity encoding on all user-generated question fields before rendering.
- Deploy a web application firewall rule to block request bodies containing script tags or JavaScript event handlers submitted to question endpoints.
- Disable web view JavaScript execution for question rendering in the Android client where feasible.
# Example CSP header to mitigate stored XSS execution
Content-Security-Policy: default-src 'self'; script-src 'self'; object-src 'none'; base-uri 'self'; frame-ancestors 'none'; report-uri /csp-report
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
