CVE-2025-63640 Overview
CVE-2025-63640 is a stored Cross-Site Scripting (XSS) vulnerability in Sourcecodester Medicine Reminder App v1.0. The application fails to sanitize user-supplied input in the Medicine Name and Notes (Optional) fields when creating an Upcoming Reminder. An attacker can inject arbitrary HTML or JavaScript that executes in the victim's browser when the Save Reminder button is clicked. The flaw is categorized under CWE-79 (Improper Neutralization of Input During Web Page Generation).
Critical Impact
Attackers can execute arbitrary JavaScript in a victim's browser session, enabling session data theft, UI manipulation, and redirection to malicious sites.
Affected Products
- Sourcecodester Medicine Reminder App version 1.0
- Component: Upcoming Reminder creation form (Medicine Name field)
- Component: Upcoming Reminder creation form (Notes (Optional) field)
Discovery Timeline
- 2025-11-07 - CVE-2025-63640 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-63640
Vulnerability Analysis
The Medicine Reminder App is a client-side JavaScript application distributed through SourceCodester. The application accepts user input through two form fields when scheduling a new reminder: Medicine Name and Notes (Optional). Neither field applies HTML encoding or input sanitization before rendering the value back into the Document Object Model (DOM). When the user submits the form by clicking Save Reminder, the injected payload is written into the reminder list and interpreted as executable HTML or JavaScript by the browser.
The defect matches the CWE-79 pattern of Improper Neutralization of Input During Web Page Generation. Successful exploitation requires user interaction, which limits automation but does not prevent targeted abuse in multi-user or shared-device deployments.
Root Cause
The root cause is missing output encoding in the reminder rendering logic. The application concatenates raw form values into HTML strings, likely via innerHTML assignment or template concatenation, instead of using safe DOM APIs such as textContent or context-aware escaping.
Attack Vector
An attacker with access to the reminder creation flow submits a payload such as an <img> tag with an onerror handler or a <script> block inside either the Medicine Name or Notes (Optional) field. Upon saving the reminder, the browser parses the injected markup and executes the attacker-controlled script in the context of the application's origin. See the vulnerability research writeup for reproduction details.
Detection Methods for CVE-2025-63640
Indicators of Compromise
- Reminder entries containing HTML tags such as <script>, <img>, <svg>, or event handler attributes (onerror, onload, onclick).
- Browser console errors or unexpected network requests originating from the reminder application page.
- Persistent storage entries (LocalStorage, IndexedDB, or backend records) containing raw markup instead of plain-text medicine names.
Detection Strategies
- Review stored reminder data for characters and sequences that should not appear in a medicine name field, including <, >, and JavaScript URI schemes.
- Deploy a Content Security Policy (CSP) in report-only mode to surface inline script execution attempts.
- Perform static analysis of the application source for unsafe sinks such as innerHTML, document.write, or insertAdjacentHTML receiving unsanitized input.
Monitoring Recommendations
- Log and alert on outbound requests from browsers loading the application to unexpected third-party domains.
- Monitor for unusual DOM mutations on the reminder listing page using browser instrumentation or synthetic testing.
- Track user-reported anomalies such as unexpected popups, redirects, or altered reminder content.
How to Mitigate CVE-2025-63640
Immediate Actions Required
- Restrict use of Sourcecodester Medicine Reminder App v1.0 in shared or multi-user environments until sanitization is implemented.
- Apply server-side and client-side input validation that rejects HTML metacharacters in the Medicine Name and Notes (Optional) fields.
- Replace unsafe DOM sinks with textContent or a vetted templating library that escapes output by default.
Patch Information
No official vendor patch is listed for CVE-2025-63640 at the time of the last NVD update on 2026-06-17. Because the codebase is distributed as sample source, operators must apply fixes locally. Refer to the CVE-2025-63640 research writeup and the original SourceCodester application listing for the affected code paths.
Workarounds
- Enforce a strict Content Security Policy that disallows unsafe-inline script execution to neutralize injected payloads.
- Sanitize stored values on read using a library such as DOMPurify before inserting them into the DOM.
- Isolate the application in a sandboxed browser profile with no access to sensitive credentials or session cookies.
# Configuration example: recommended Content Security Policy header
Content-Security-Policy: default-src 'self'; script-src 'self'; object-src 'none'; base-uri 'self'; frame-ancestors 'none'
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
