🔒 Security Report: Reflective XSS Vulnerability with Account Takeover Potential 🔒

We want to bring attention to a critical security vulnerability that recently came across our radar. In today’s digital landscape, safeguarding user data is paramount, and we must remain vigilant in identifying and mitigating risks.

Summary: We’ve uncovered a reflected cross-site scripting (XSS) vulnerability within an application’s /auth/v2/login/signin endpoint. This vulnerability allows malicious actors to inject JavaScript code into the return_to parameter, potentially leading to account takeover and other malicious activities.

Vulnerability Details:

• Endpoint: /auth/v2/login/signin
• Parameter: return_to

Vulnerable Code: The issue stems from improper user input validation, which enables attackers to inject arbitrary JavaScript code into the return_to parameter.

/auth/v2/login/signin?return_to={{PAYLOAD}}&theme=hc&locale=1&brand_id={{BRAND_ID}}&auth_origin={{AUTH_ORIGIN}}

Payload: An attacker could use a payload like this to exploit the vulnerability:

javascript:alert(document.cookie)

Evolving from XSS to Account Takeover: This vulnerability is not just about executing a simple alert. It poses a significant risk because it can escalate from an XSS attack to an account takeover scenario. Here’s how:

1. Initial XSS: The attacker injects malicious JavaScript code as described in the payload.
2. Session Hijacking: By stealing the victim’s session cookies, the attacker can effectively hijack the user’s session and impersonate them.
3. Change Password: With session control, the attacker can change the victim’s password, locking them out of their own account.
4. Total Control: Now in full control of the account, the attacker can access sensitive information, perform unauthorized actions, and even escalate privileges.

Recommendations: To mitigate this vulnerability, it is essential to:

• Sanitize Input: Ensure rigorous validation of user-supplied input.
• Output Encoding: Apply proper output encoding to prevent script execution.
• Security Headers: Implement Content Security Policy (CSP) headers.
• User Education: Educate users about the risks of clicking on suspicious links and advise enabling 2FA for added security.

Proof of Concept (PoC): We’ve included a PoC to demonstrate the vulnerability. You can follow the steps mentioned in our detailed report to witness the XSS vulnerability in action.

Navigate to the login of your application.

Modify the return_to={{your_value}} parameter to javascript:alert(1).

Login and observe XSS payload to popup.

Security is a shared responsibility. By identifying and addressing vulnerabilities like this, we can collectively create a safer digital environment for everyone. 💪💻

We encourage you to share your thoughts and insights on this topic. Let’s continue the conversation and work together to enhance digital security. 🚀