CVE-2015-20106 in ClickBank Affiliate Ads Plugin
Summary
by MITRE • 12/02/2021
The ClickBank Affiliate Ads WordPress plugin through 1.20 does not escape its settings, allowing high privilege users to perform Cross-Site Scripting attacks even when the unfiltered_html is disallowed.
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Analysis
by VulDB Data Team • 12/08/2021
The vulnerability identified as CVE-2015-20106 affects the ClickBank Affiliate Ads WordPress plugin version 1.20 and earlier, presenting a critical cross-site scripting weakness that undermines the security posture of affected WordPress installations. This vulnerability specifically targets the plugin's handling of administrative settings, where insufficient output escaping mechanisms allow malicious actors with elevated privileges to inject malicious scripts into the plugin's configuration interface. The flaw is particularly concerning because it operates even when the WordPress installation has properly restricted the unfiltered_html capability, which is a standard security measure designed to prevent unrestricted HTML injection in administrative contexts.
The technical exploitation of this vulnerability occurs through the improper sanitization of user-supplied input within the plugin's settings management functionality. When administrators access the plugin configuration interface, the stored settings are rendered back to the browser without adequate HTML escaping, creating an environment where malicious scripts can execute in the context of the authenticated administrator's session. This scenario enables attackers with access to administrative accounts to perform persistent cross-site scripting attacks that can potentially escalate to full system compromise. The vulnerability maps directly to CWE-79, which describes cross-site scripting flaws where untrusted data is improperly incorporated into web pages without adequate validation or escaping mechanisms. The attack vector leverages the principle of least privilege violation, as the malicious scripts execute with the elevated permissions of the administrator, potentially enabling unauthorized modifications to plugin settings, data exfiltration, or session hijacking.
The operational impact of this vulnerability extends beyond simple script execution, as it can enable attackers to manipulate the plugin's functionality and potentially gain access to sensitive administrative data. An attacker could inject malicious JavaScript code that modifies affiliate link tracking parameters, alters revenue reporting, or redirects users to malicious domains while maintaining persistent access through the compromised administrative session. The vulnerability also presents risks to the broader WordPress ecosystem, as successful exploitation could lead to privilege escalation attacks that might compromise other plugins or themes within the same installation. According to ATT&CK framework, this vulnerability aligns with T1059.001 (Command and Scripting Interpreter: PowerShell) and T1566 (Phishing) techniques, as attackers could use the XSS payload to redirect users to phishing pages or execute malicious commands through PowerShell scripts. The vulnerability's persistence is enhanced by the fact that the malicious scripts are stored within the plugin's settings, making them resistant to temporary session termination and requiring explicit removal of the malicious code from the configuration.
Mitigation strategies for this vulnerability must address both immediate remediation and long-term security improvements. The primary solution involves updating to a patched version of the ClickBank Affiliate Ads plugin where proper output escaping has been implemented for all user-controllable settings. Administrators should also implement additional security measures including regular security audits of installed plugins, enforcement of the wp_kses function for all user-generated content, and implementation of Content Security Policy headers to limit script execution. The WordPress security community recommends maintaining an updated inventory of all installed plugins and themes, as well as implementing automated scanning tools to detect similar output escaping vulnerabilities in custom or third-party code. Organizations should also consider implementing web application firewalls to detect and block suspicious script injection attempts, and establish regular security training for administrators to recognize potential phishing attempts that might leverage such vulnerabilities. The vulnerability demonstrates the critical importance of proper input validation and output escaping in web applications, particularly in administrative interfaces where privilege levels are elevated and the potential for damage is significantly increased.