CVE-2011-5106 in Flexible Custom Post Type
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in edit-post.php in the Flexible Custom Post Type plugin before 0.1.7 for WordPress allows remote attackers to inject arbitrary web script or HTML via the id parameter.
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Analysis
by VulDB Data Team • 02/01/2025
The CVE-2011-5106 vulnerability represents a classic cross-site scripting flaw within the Flexible Custom Post Type plugin for WordPress, specifically affecting versions prior to 0.1.7. This vulnerability exists in the edit-post.php script and allows remote attackers to execute malicious scripts or HTML code through manipulation of the id parameter. The issue stems from insufficient input validation and output sanitization within the plugin's administrative interface, creating a pathway for attackers to inject malicious content that can be executed in the context of other users' browsers. Such vulnerabilities are particularly dangerous in content management systems where administrators and users interact with potentially untrusted content, as they can lead to session hijacking, data theft, or further exploitation of the compromised system.
The technical exploitation of this vulnerability occurs when an attacker crafts a malicious URL containing crafted script code within the id parameter of the edit-post.php endpoint. When an authenticated administrator or user with sufficient privileges accesses this malformed URL, the malicious script executes in their browser context, potentially stealing cookies, session tokens, or performing unauthorized actions on behalf of the victim. The vulnerability directly maps to CWE-79, which describes Cross-site Scripting flaws where untrusted data is improperly incorporated into web page content without proper sanitization or encoding. This weakness allows attackers to bypass the browser's security restrictions and execute arbitrary code within the victim's browser environment, making it a significant concern for WordPress administrators who rely on third-party plugins for extended functionality.
The operational impact of CVE-2011-5106 extends beyond simple script injection, as it can enable sophisticated attack vectors within WordPress environments. An attacker who successfully exploits this vulnerability can potentially escalate privileges, steal administrative credentials, or manipulate content management workflows. The vulnerability is particularly concerning in multi-user WordPress installations where administrators have elevated privileges and access to sensitive system information. From an attack framework perspective, this vulnerability aligns with ATT&CK technique T1566.001, which covers credential harvesting through social engineering, as attackers can use XSS to steal session cookies and gain unauthorized access to administrative accounts. The vulnerability also represents a pathway for lateral movement within compromised WordPress environments, as successful exploitation can lead to broader system compromise.
Mitigation strategies for CVE-2011-5106 should focus on immediate plugin updates to version 0.1.7 or later, which contain the necessary patches to address the input validation issues. Administrators should also implement comprehensive input sanitization measures, including proper escaping of output data and validation of all user-supplied parameters. Network-level protections such as web application firewalls can provide additional layers of defense by detecting and blocking malicious script injection attempts. Regular security audits of installed plugins and themes are essential to identify and remediate similar vulnerabilities before they can be exploited. The vulnerability highlights the importance of maintaining up-to-date WordPress installations and third-party components, as outdated software represents a significant attack surface for malicious actors seeking to exploit known weaknesses in the system architecture.