# Cross-Site Scripting (XSS) Analysis Report

## 1. Executive Summary

- **Analysis Status:** Complete  
- **Key Outcome:** **NO exploitable XSS vulnerabilities found.** All potential XSS sinks are adequately protected by context-appropriate defenses (Jinja2 auto-escaping and safe DOM APIs). However, **GraphQL injection vulnerabilities** were identified in client-side query construction, which are distinct from XSS but represent serious security flaws.
- **Purpose of this Document:** This report provides comprehensive analysis of all identified XSS sinks, explains why they are not exploitable for XSS, and documents the GraphQL injection findings for awareness.

## 2. Dominant Vulnerability Patterns

### Pattern 1: GraphQL Injection via Client-Side String Interpolation (NOT XSS)

- **Description:** The application constructs GraphQL queries using JavaScript template literals with direct string interpolation of user input. This allows attackers to inject GraphQL syntax and manipulate query structure. However, this is **GraphQL injection, not XSS**.
- **Locations:** 
  - `/app/templates/add_prescription.html:24` - `prescriptionDetails` parameter
  - `/app/templates/view_prescriptions.html:26` - `userID` parameter
- **Impact:** Information disclosure, authorization bypass, schema introspection - but **not client-side code execution (XSS)**.
- **XSS Relationship:** These vulnerabilities do NOT lead to XSS because the GraphQL API responses are not reflected unsafely into the DOM.

### Pattern 2: Secure DOM Rendering via .innerText

- **Description:** All user-controlled data rendered to the DOM uses the `.innerText` property, which treats content as plain text and automatically escapes HTML/JavaScript.
- **Location:** `/app/templates/view_prescriptions.html:43`
- **Implication:** Stored XSS attempts are neutralized - malicious HTML/JavaScript payloads are displayed as harmless text.
- **Verification:** Tested with payload `<img src=x onerror=alert(1)>` - rendered as literal text, not executed.

### Pattern 3: Jinja2 Auto-Escaping for Template Variables

- **Description:** Server-side Jinja2 templates have auto-escaping enabled by default in Flask. All template variables are HTML-encoded before rendering.
- **Location:** `/app/templates/view_prescriptions.html:4` - username rendering
- **Implication:** Even if an attacker could inject malicious usernames into the database, they would be HTML-escaped and not execute as JavaScript.
- **Additional Protection:** No user registration mechanism exists, so username is not attacker-controllable through the application interface.

## 3. Strategic Intelligence for Exploitation

**Content Security Policy (CSP) Analysis**  
- **Current CSP:** None detected
- **Impact:** No CSP protection exists, but this is moot since no XSS vulnerabilities were found
- **Note:** If XSS were present, lack of CSP would make exploitation trivial

**Cookie Security**  
- **Session Cookie Flags:** The session cookie does not have HttpOnly flag set (confirmed in reconnaissance)
- **Impact for XSS:** If XSS existed, session cookies would be stealable via `document.cookie`
- **Current Status:** No XSS found, so this weakness cannot be exploited for session theft via XSS

**DOM-Based XSS Surface**  
- **Client-Side JavaScript Complexity:** Minimal - only prescription display and form submission logic
- **Dangerous Sinks Searched:** `innerHTML`, `outerHTML`, `document.write`, `eval`, `Function()`, `setTimeout(string)`, `location.href` assignment
- **Findings:** Only safe APIs used (`.innerText`, `.textContent`)

## 4. Vectors Analyzed and Confirmed Secure

| Source (Parameter/Key) | Endpoint/File Location | Defense Mechanism Implemented | Render Context | Verdict |
|------------------------|------------------------|-------------------------------|----------------|---------|
| `prescriptionDetails` (storage) | `/api` → Database → `/view_prescriptions` | `.innerText` DOM API (auto-escapes HTML) | HTML_BODY | SAFE |
| `username` (template variable) | `/view_prescriptions` template | Jinja2 auto-escaping (enabled by default) | HTML_BODY | SAFE |
| `userID` (client-side) | `/view_prescriptions.html:26` | Not reflected in DOM; used only for GraphQL query construction | N/A - Not rendered | SAFE (from XSS) |
| `prescriptionDetails` (input) | `/add_prescription.html:24` | Not reflected in DOM; used only for GraphQL mutation | N/A - Not rendered | SAFE (from XSS) |

## 5. Analysis Constraints and Blind Spots

### Application Architecture Limitations

**Broken Client-Side Code:**
- The `userID` variable is undefined in both `/add_prescription.html` and `/view_prescriptions.html` due to a coding error
- The Flask backend passes `userID` to Jinja2 templates, but the JavaScript never renders it with `{{ userID }}`
- This breaks normal functionality but also prevented complete testing of some code paths
- **XSS Impact:** This bug does not create XSS vulnerabilities; it actually prevents some client-side code from executing

**No User Registration:**
- The application has no registration endpoint, limiting attack surface
- Usernames are hardcoded in `init_db()` function
- This eliminates the primary vector for Stored XSS via user-controlled profile data

### XSS Sinks Analyzed

**Traditional XSS Sinks Searched (0 Found):**
- `eval()` - Not found
- `Function()` constructor - Not found
- `document.write()` / `document.writeln()` - Not found
- `innerHTML` assignment with user data - Not found (only used with empty string `""`)
- `outerHTML` assignment - Not found
- `setTimeout()` / `setInterval()` with string arguments - Not found
- Event handler attributes (`onclick`, `onerror`, etc.) with user data - Not found
- `location.href` assignment with user input - Not found
- `window.open()` with user input - Not found
- jQuery `.html()` method - Not applicable (uses jQuery slim which excludes this method)

**Template Injection:**
- Server-Side Template Injection (SSTI) - Not vulnerable
- All Jinja2 templates use variable rendering (`{{ variable }}`), not expression evaluation
- No user-controlled data in `{% %}` blocks
- Auto-escaping prevents XSS even if template variables were controllable

## 6. GraphQL Injection Findings (Non-XSS)

While not XSS vulnerabilities, the following GraphQL injection issues were discovered during analysis:

### GraphQL Injection #1: prescriptionDetails Parameter
- **File:** `/app/templates/add_prescription.html:24`
- **Vulnerability:** Direct string interpolation in GraphQL mutation
- **Pattern:** `` prescriptionDetails: "${prescriptionDetails}" ``
- **Impact:** GraphQL injection, information disclosure, not XSS
- **Reason Not XSS:** Response is not reflected in DOM unsafely

### GraphQL Injection #2: userID Parameter
- **File:** `/app/templates/view_prescriptions.html:26`
- **Vulnerability:** Undefined variable allows global scope pollution
- **Pattern:** `` getPrescriptions(userId: ${userID}) ``
- **Impact:** GraphQL injection, authorization bypass, not XSS
- **Reason Not XSS:** Response rendered via safe `.innerText` API

**Note:** These findings should be addressed by the Injection Analysis Specialist, not the XSS Exploitation phase.

## 7. Conclusion

**No exploitable XSS vulnerabilities exist in the MedGuard application.** The application demonstrates secure coding practices in output encoding:
1. **Client-side DOM manipulation** uses safe APIs (`.innerText`, `.textContent`)
2. **Server-side templating** leverages Jinja2 auto-escaping
3. **User-controlled data** has no direct path to dangerous DOM sinks

The GraphQL injection vulnerabilities identified are serious security issues but are distinct from XSS and do not enable client-side code execution in the victim's browser.

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**Analysis Completion Date:** 2025-01-27  
**Analyst:** XSS Analysis Specialist  
**Next Phase:** No XSS Exploitation phase required (no vulnerabilities found)