Compliance Impact

The vulnerability allows an attacker to execute arbitrary JavaScript code in the victim's browser after login, potentially leading to session hijacking, credential theft, or unauthorized actions.

Such security flaws can impact compliance with standards like GDPR and HIPAA because they may lead to unauthorized access to personal or sensitive data, violating data protection and privacy requirements.

Failure to address this vulnerability could result in breaches of confidentiality and integrity of user data, which are critical compliance aspects under these regulations.

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Executive Summary

This vulnerability is a DOM-based Cross-Site Scripting (XSS) issue found in the sign-in auto-redirect functionality of Pingvin Share. It occurs because the application improperly trusts and uses a URL parameter named "redirect" without sanitization. An attacker can craft a malicious link with a JavaScript payload in this redirect parameter. When a victim, who is already authenticated, clicks this link and logs in, the malicious script executes in their browser.

The root cause is that the application does not sanitize the redirect parameter before performing a client-side redirect, allowing execution of JavaScript via the "javascript:" protocol.

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Impact Analysis

Exploitation of this vulnerability can lead to serious security impacts such as session hijacking, credential theft, or unauthorized actions performed on behalf of the victim user.

Since the attack requires the victim to be authenticated, it targets logged-in users and can compromise their accounts by executing arbitrary code in their browsers.

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Detection Guidance

This vulnerability can be detected by monitoring for usage of the "redirect" URL parameter in the sign-in process of Pingvin Share, specifically in the sign-in auto-redirect functionality. Look for URLs containing the "redirect" parameter with suspicious or JavaScript payloads such as those starting with "javascript:".

You can use web server logs or proxy logs to search for requests containing the redirect parameter with potentially malicious content.

• Example command to search web server logs for suspicious redirect parameters (Linux):
• grep -i 'redirect=javascript:' /var/log/nginx/access.log
• Or to find any redirect parameters in logs:
• grep -i 'redirect=' /var/log/nginx/access.log

Additionally, manual testing can be performed by attempting to access the sign-in page with a crafted URL containing a JavaScript payload in the redirect parameter to see if the payload executes after login.

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Mitigation Strategies

Immediate mitigation steps include sanitizing the "redirect" parameter before it is used in the client-side redirect to prevent execution of JavaScript payloads.

If you have access to the source code, apply a safe redirect function that validates and restricts the redirect parameter to only allow safe URLs or relative paths.

Until a patch is available, consider implementing web application firewall (WAF) rules to block requests containing suspicious redirect parameters, especially those starting with "javascript:".

Also, educate users to be cautious about clicking on suspicious links containing redirect parameters.

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