Clickjacking DOM XSS Vulnerability on Google.org

The Google Crisis Map project is an underutilized but noteworthy Google initiative designed to provide vital emergency information to users worldwide. Originally launched in 2012, this tool enabled individuals and organizations to create and share critical maps related to crises such as natural disasters and other emergencies.

While the platform remains operational, it is infrequently updated, making it an attractive target for security researchers interested in uncovering vulnerabilities within legacy applications maintained by major organizations.

Overview of the Google.org Domain and Security Implications

Although the Crisis Map is hosted on the google.org domain—which generally has lower severity concerns compared to google.com regarding client-side vulnerabilities—it still represents a Google-owned asset requiring robust security measures. Legacy projects like these can inadvertently contain security flaws due to infrequent updates or less stringent protections.

Accessing and Managing the Crisis Map

Visiting google.org/crisismap redirects users to the default interactive map titled “Weather and Events.” This read-only map offers basic viewing functionality without permitting edits or content management.

To access map management and creation features, append .maps to the URL, navigating to google.org/crisismap/.maps. Users must authenticate with a Google account, gaining access to a dashboard displaying default and user-created maps.

Creating Maps and Domain Restrictions

When attempting to create a new map, users logging in with a standard gmail.com account receive an error blocking map creation. This restriction enforces using GSuite or custom domain emails for map publishing. After successful authentication with an allowed domain, users can create new maps and access editing tools.

Discovery of the DOM-based Cross-Site Scripting (XSS) Vulnerability

Adding Layers with Potentially Malicious URLs

Within the map editor, users can add layers by specifying titles and source URLs. Testing with a value like javascript:alert(document.domain) in the “Source URL” field triggers a client-side validation error requiring protocol inclusion (e.g., http:// or https://).

The frontend code implements a simplistic regular expression validating the URL protocol, but this check is not enforced server-side, presenting an opportunity for exploitation.

Bypassing Frontend Validation via Request Modification

Security testing tools such as Fiddler or Burp Suite enable intercepting and modifying HTTP requests. By submitting a valid URL first (e.g., https://example.com), then altering the JSON payload in the POST request to the maps API, the javascript: scheme can be reintroduced, bypassing frontend restrictions.

POST https://google.org/crisismap/.api/maps/1234

{
  "id": "1234",
  "title": "Untitled map",
  "base_map_type": "GOOGLE_ROADMAP",
  "layers": [{
    "id": "1",
    "title": "Test layer",
    "visibility": "DEFAULT_ON",
    "type": "KML",
    "source": {
      "kml": {
        "url": "javascript:alert(document.domain)"
      }
    }
  }]
}

Exploitation and XSS Testing

Upon saving the modified map, reloading the interface and navigating to the “Layers” tab reveals a “Download KML” link containing the malicious javascript: URL. Clicking this link triggers a JavaScript alert, confirming the existence of a Document Object Model-based Cross-Site Scripting vulnerability.

Mitigation Approaches Adopted by Google

Rather than reinforcing backend URL validation, Google addressed the issue by sanitizing the URL before embedding it into the DOM. If the URL failed validation, it was replaced with a safe placeholder such as about:invalid, preventing malicious JavaScript execution on page interaction.

<a href="about:invalid#zClosurez">Download KML</a>

Impact Analysis and Severity Assessment

This XSS vulnerability was initially classified as a self-XSS since only the authenticated user who created the map could trigger the payload. The requirement for login and map editing permissions limited its immediate risk.

However, users can publish their maps publicly via URLs such as https://google.org/crisismap/example.com/test. In this scenario, any visitor could access the page, potentially execute the XSS payload, and increase the vulnerability’s severity.

Despite this, the user must perform multiple actions (open “Layers” and click “Download KML”) for the exploit to trigger, limiting the attack’s practicality.

Leveraging Clickjacking to Elevate the Attack

A critical factor enabling an escalation of this vulnerability was the omission of the X-Frame-Options HTTP header in responses from the google.org domain. This header instructs browsers whether a page can be embedded in frames or iframes, mitigating clickjacking risks.

What is Clickjacking?

Clickjacking is an attack technique where a malicious site overlays invisible or deceptive UI elements on trustworthy websites loaded inside iframes, tricking users into performing unintended actions.

Because google.org responses lacked X-Frame-Options, an attacker could embed published maps within an iframe on their site, overlay controls using CSS, and simulate clicks to execute the XSS payload without the user navigating away.

By scaling and positioning the iframe strategically, the victim could inadvertently click through the necessary steps (“Layers” tab and “Download KML” link) seamlessly — effectively transforming a multi-step self-XSS into a more dangerous clickjacking-mediated exploit.

Visual Demonstration

The original proof-of-concept used CSS to scale the iframe by 50× and reposition clicks precisely, with an opaque overlay ensuring users were unaware of the embedded Google content beneath. Though the live demo is discontinued with Google Crisis Map, the concept remains instructive for similar vulnerabilities.

Key Lessons and Security Best Practices

1. Never trust client-side validation alone. Robust backend validation and sanitization of user inputs are essential to prevent injection attacks, including XSS.
2. Implement strict frame-busting measures. Set HTTP headers like X-Frame-Options or Content Security Policy (CSP) frame-ancestors directives to prevent unauthorized embedding and mitigate clickjacking risks.
3. Prioritize vulnerability severity escalation. When identifying security flaws, explore avenues to amplify impact, such as exploiting misconfigurations or chaining vulnerabilities toward account takeovers or data leakage, to better comprehend risk.
4. Review legacy and lower-profile projects. Often overlooked older applications remain in use and can harbor significant vulnerabilities, representing low-hanging fruit for researchers and attackers alike.

Contextualizing with Broader Research and Trends

The ongoing challenges in defending against XSS and clickjacking attacks remain prominent globally. According to the 2023 OWASP Top 10 report, injection flaws—including XSS—consistently rank among the most critical web application security risks.

Similarly, PortSwigger Web Security Academy highlights how improper framing protections can drastically increase attack surfaces, especially when combined with client-side vulnerabilities.

The Google Crisis Map incident serves as a case study reinforcing that even tech giants must apply rigorous layered defenses to maintain secure online services.

Conclusion

In summary, the Clickjacking DOM XSS vulnerability in Google.org’s Crisis Map underscores the importance of comprehensive input validation, securing HTTP headers, and understanding how seemingly minor gaps can combine into impactful security weaknesses.

While Google has mitigated this specific issue, the principles and attack techniques demonstrated remain widely applicable to modern web application security.

Staying vigilant about legacy web assets, enforcing backend validation, and preventing clickjacking via frame restrictions are crucial steps to safeguard users and maintain trust in digital platforms.