Technical Analysis of HackerOne Report #502758: Google XSS Exploit via Translator Widget
Overview:
This report outlines the discovery of a Cross-Site Scripting (XSS) vulnerability on a Google subdomain that hosts the Google Translator widget (translate.googleusercontent.com). The vulnerability was serious enough to merit a $5,000 reward from Google. The report is detailed, showcasing the thought process and steps taken to exploit this vulnerability.
Key Technical Details:
- Identifying the Vulnerability Vector:
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The researcher identified that the Google Translator widget, located on
translate.googleusercontent.com, was prone to XSS. This widget is used to embed translation features on a third-party website. -
Exploit Development:
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The attack vector involved finding a way to inject JavaScript into a webpage translated by Google Translate. The widget fetches the original webpage's content and performs translation on it. During this process, it appeared that JavaScript payloads embedded within the content could execute.
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Injection Mechanism:
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The researcher embedded a malicious script in an HTML page and used the Google Translate widget to translate this page. The translation process mishandled the embedded script, thereby executing it.
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Bypassing CSP (Content Security Policy):
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Google's Translator subdomain used a secure CSP to mitigate common injection attacks. The research demonstrated that the translation mechanism didn't properly sanitize the HTML content during translation, which allowed the JavaScript payload to execute despite CSP.
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Executable Payload:
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The malicious payload was a simple script embedded inside an HTML page. When this page was translated by the widget, the script executed, thereby achieving XSS. Example payload:
html <html> <body> <script>alert(document.domain)</script> </body> </html> -
Impact:
- The XSS vulnerability allowed for arbitrary script execution on
translate.googleusercontent.com. Given the trusted nature of Google's domain, this could lead to session hijacking, phishing, or further exploitative actions against users visiting the affected pages.
Key Takeaways:
- Widget Risks: Embedding third-party widgets poses significant security challenges, especially if the widget processes and renders user-controlled content.
- Sanitization: It is crucial to sanitize all input thoroughly, especially when processing HTML content from external sources.
- CSP Limitations: Content Security Policies (CSP) provide an additional layer of security but are not foolproof. They should be part of a defense-in-depth strategy, complemented by rigorous input validation and sanitization protocols.
- Scope of XSS: The vulnerability on a trusted domain like Google expands the potential impact of seemingly trivial XSS bugs. Trust and reputation of domains can amplify the consequences of an XSS attack.
Conclusion:
This report underscores the necessity of secure programming practices, especially when dealing with user-supplied content across various domains. It highlights how even well-established, secure platforms can harbor vulnerabilities. Developers of web applications, especially those involving third-party content or translations, should ensure comprehensive sanitization and testing to prevent such exploits.
For additional details and the original report, visit HackerOne Report #502758.