My auctions allegro <= 3.6.34 - Reflected Cross-Site Scripting

This research plan outlines the steps to identify and exploit a Reflected Cross-Site Scripting (XSS) vulnerability in the My auctions allegro plugin (versions <= 3.6.34).

1. Vulnerability Summary

The "My auctions allegro" plugin fails to properly sanitize or escape user-supplied input from HTTP GET parameters before echoing them back into the HTML response. This occurs in the context of administrative pages or potentially public-facing auction displays. An attacker can craft a malicious URL containing a JavaScript payload; if a logged-in user (typically an administrator) clicks this link, the script executes in their browser session.

2. Attack Vector Analysis

• Endpoint: wp-admin/admin.php (for admin-side reflection) or a page containing the plugin's shortcode.
• Vulnerable Parameter: Likely s, tab, msg, error, or id (inferred).
• Authentication: Unauthenticated (to craft and send the link), but requires a victim (Admin) to click it for high-impact exploitation.
• Preconditions: The plugin must be active. For admin-side XSS, the victim must have an active session.

3. Code Flow

1. The plugin registers an admin menu page via add_menu_page() or add_submenu_page() (likely in a file like my-auctions-allegro.php or includes/admin.php).
2. The callback function for this menu page is triggered when wp-admin/admin.php?page=my-auctions-allegro... is visited.
3. Inside the callback, the code retrieves a parameter from the global $_GET or $_REQUEST array.
4. The value is directly printed using echo or printf without passing through esc_html(), esc_attr(), or wp_kses().
5. Sink: echo $_GET['parameter_name'];

4. Nonce Acquisition Strategy

Reflected XSS in a GET parameter typically occurs during the rendering phase and often does not require a nonce, as it is not a state-changing operation (like a POST request). However, if the reflection is inside a form that uses a nonce, the reflection itself usually happens before/regardless of the nonce check.

If the agent finds that a nonce is required to reach the vulnerable code path:

1. Identify Shortcode: Search for add_shortcode in the plugin: grep -r "add_shortcode" ..
2. Setup Page: Create a page containing that shortcode:
   wp post create --post_type=page --post_status=publish --post_content='[my-auctions-allegro-shortcode]'
3. Navigate: Use browser_navigate to visit the newly created page.
4. Extract: Look for a localized script containing a nonce.
   • Example: browser_eval("window.maa_vars?.nonce") (inferred variable name).
   • Verify the variable name by searching the source for wp_localize_script.

5. Exploitation Strategy

Step 1: Locate the Reflection Point
The agent should first use grep to find unescaped output of GET parameters:

grep -rP "echo.*\$_GET\[" .
grep -rP "echo.*\$_REQUEST\[" .

Step 2: Identify the Admin Page
Determine the admin slug to target:

grep -r "add_menu_page" .

Step 3: Craft the Payload
Based on the identified parameter (e.g., tab), craft a Reflected XSS URL.

• Target URL: http://localhost:8080/wp-admin/admin.php?page=[SLUG]&[PARAM]=[PAYLOAD]
• Payload 1 (Simple): <script>alert(window.origin)</script>
• Payload 2 (Attribute Breakout): "><script>alert(1)</script>

Step 4: Execute the Exploit
Use the http_request tool or browser_navigate (to simulate the admin clicking the link). Since this is Reflected XSS, browser_navigate is preferred to "see" the execution.

// Example call for the agent
browser_navigate("http://localhost:8080/wp-admin/admin.php?page=my-auctions-allegro&tab=<script>console.log('XSS_SUCCESS')</script>");

6. Test Data Setup

1. Install Plugin: Ensure my-auctions-allegro-free-edition version 3.6.34 is installed and active.
2. Administrator User: Use the existing admin credentials for the browser_navigate session.
3. Content: If the reflection is on the frontend, create a post with the plugin's main shortcode (e.g., [my-auctions-allegro]).

7. Expected Results

• When navigating to the crafted URL, the browser should execute the injected script.
• In a test environment, this is confirmed by checking the console logs for a specific string (e.g., XSS_SUCCESS) or an alert box being triggered.
• The HTML source of the rendered page will contain the raw payload instead of an escaped version (e.g., <script> instead of <script>).

8. Verification Steps

1. Source Check: After the http_request, check the body for the unescaped payload:
   grep "<script>alert(1)</script>" response_body.html
2. Browser Verification: Use browser_eval to check if a global variable set by the payload exists:
   browser_eval("window.xss_executed = true;")
3. Manual Code Review: Verify the file and line number identified by grep to confirm no sanitization functions are present.

9. Alternative Approaches

If simple reflection in $_GET isn't found, check for:

• $_SERVER['REQUEST_URI']: Often reflected in form actions.
  • Payload: /wp-admin/admin.php/page=slug?param="><script>alert(1)</script>
• $_SERVER['PHP_SELF']: Similar to above.
• Shortcode Attributes: If the plugin reflects attributes passed in a shortcode without escaping, an attacker with "Contributor" or "Author" permissions could achieve Stored XSS, which is often related to reflected sanitization failures.