CVE-2015-9439 in addthis Plugin
Summary
by MITRE
The addthis plugin before 5.0.13 for WordPress has CSRF with resultant XSS via the wp-admin/options-general.php?page=addthis_social_widget pubid parameter.
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Analysis
by VulDB Data Team • 12/28/2023
The CVE-2015-9439 vulnerability represents a critical security flaw in the AddThis plugin for WordPress systems, specifically affecting versions prior to 5.0.13. This vulnerability combines elements of Cross-Site Request Forgery and Cross-Site Scripting attacks, creating a particularly dangerous exploit vector for WordPress administrators. The flaw resides within the plugin's handling of the pubid parameter in the wp-admin/options-general.php?page=addthis_social_widget endpoint, which allows malicious actors to manipulate the plugin's configuration through crafted requests that appear legitimate to the WordPress admin interface.
The technical implementation of this vulnerability stems from inadequate input validation and missing CSRF protection mechanisms within the AddThis plugin's administrative interface. When an administrator visits the plugin settings page, the pubid parameter is processed without proper sanitization or verification of the request source. This allows attackers to craft malicious requests that, when executed by an authenticated administrator, can inject arbitrary JavaScript code into the WordPress admin environment. The vulnerability specifically targets the plugin's configuration handling where the pubid parameter is used to store publisher identification information, which is then rendered without proper HTML escaping in subsequent administrative displays.
The operational impact of CVE-2015-9439 extends beyond simple data theft or defacement, as it provides attackers with a pathway to establish persistent access to WordPress installations. Once an administrator is tricked into executing a malicious request, the injected XSS payload can be used to steal admin session cookies, modify plugin configurations, or even install backdoors. This vulnerability directly aligns with CWE-352, which categorizes Cross-Site Request Forgery flaws, and CWE-79, which addresses Cross-Site Scripting vulnerabilities. The combined nature of these flaws creates a particularly potent attack scenario where the CSRF element enables the execution of malicious requests, while the XSS component provides the payload delivery mechanism for more sophisticated attacks.
The attack surface for this vulnerability is significant within WordPress ecosystems, particularly in environments where multiple administrators have access to plugin management interfaces. The exploitation requires social engineering to convince administrators to visit malicious websites or click on compromised links, but once successful, provides attackers with elevated privileges within the WordPress installation. This vulnerability also maps to several ATT&CK techniques including T1059 for command and control through script injection, T1071 for application layer protocol usage, and T1546 for persistence mechanisms. Organizations running affected versions of the AddThis plugin face substantial risk of compromise, as the vulnerability can be exploited without requiring elevated privileges beyond basic WordPress administrator access, making it particularly dangerous in shared hosting environments or multi-user WordPress installations where administrator access is more prevalent.
Mitigation strategies for CVE-2015-9439 require immediate action including upgrading to version 5.0.13 or later of the AddThis plugin, which implements proper CSRF tokens and input sanitization. Administrators should also consider implementing additional security measures such as role-based access controls, regular security audits of installed plugins, and monitoring for unauthorized configuration changes. The vulnerability highlights the importance of maintaining current plugin versions and implementing proper input validation practices within WordPress plugin development. Organizations should conduct thorough security assessments of their WordPress installations to identify other potentially vulnerable plugins and ensure that all administrative interfaces properly implement CSRF protection mechanisms. Additionally, implementing Content Security Policy headers and regular security scanning can provide additional layers of defense against similar vulnerabilities in the future.