CVE-2017-6215 in permissions-sdk-php
Summary
by MITRE
paypal/permissions-sdk-php is vulnerable to reflected XSS in the samples/GetAccessToken.php verification_code parameter, resulting in code execution.
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Analysis
by VulDB Data Team • 04/29/2023
The vulnerability identified as CVE-2017-6215 affects the paypal/permissions-sdk-php library and represents a reflected cross-site scripting flaw within the samples/GetAccessToken.php script. This issue specifically targets the verification_code parameter, which serves as an entry point for malicious input that can be exploited to execute arbitrary code within the context of a user's browser session. The vulnerability resides in the sample implementation rather than the core library, making it particularly concerning for developers who may implement similar patterns without proper input sanitization.
The technical nature of this flaw aligns with CWE-79, which describes cross-site scripting vulnerabilities where untrusted data is incorporated into web pages without proper validation or encoding. The reflected XSS occurs because the verification_code parameter is directly echoed back to the user without adequate sanitization or output encoding mechanisms. When an attacker crafts a malicious URL containing crafted script tags within the verification_code parameter, these scripts execute in the victim's browser when the page loads, potentially leading to session hijacking, credential theft, or other malicious activities.
The operational impact of this vulnerability extends beyond simple script execution, as it can enable attackers to perform actions on behalf of authenticated users within the PayPal ecosystem. The reflected nature of the vulnerability means that the attack vector typically involves social engineering to convince victims to click on malicious links. This vulnerability can be particularly dangerous in environments where users have elevated privileges or where the application integrates with sensitive payment processing systems. The attack requires minimal sophistication and can be automated, making it a significant risk for any implementation that does not properly validate or sanitize user input before incorporating it into web responses.
Organizations should implement comprehensive input validation and output encoding mechanisms to prevent this class of vulnerability from occurring. The recommended mitigations include implementing strict parameter validation that rejects or sanitizes potentially malicious input, utilizing proper output encoding for all user-supplied data before rendering it in web responses, and implementing content security policies to limit script execution. Additionally, developers should follow the principle of least privilege when implementing sample code and ensure that such code does not inadvertently expose security flaws that could be copied or adapted by other developers. This vulnerability demonstrates the critical importance of securing not just the core functionality but also sample implementations that are often used as templates by developers without proper security review. The ATT&CK framework categorizes this under T1203, which involves exploiting web applications to execute malicious code, emphasizing the need for robust web application security controls and regular security assessments of all application components including sample code implementations.