CVE-2015-4139 in WP Smiley Plugin
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in smilies4wp.php in the WP Smiley plugin 1.4.1 for WordPress allows remote authenticated users to inject arbitrary web script or HTML via the s4w-more parameter to wp-admin/options-general.php.
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Analysis
by VulDB Data Team • 04/09/2019
The CVE-2015-4139 vulnerability represents a critical cross-site scripting flaw within the WP Smiley plugin version 1.4.1 for WordPress platforms. This security weakness specifically targets the smilies4wp.php component and manifests through improper input validation mechanisms that fail to adequately sanitize user-supplied data. The vulnerability affects authenticated users who possess sufficient privileges to access the WordPress administrative interface, making it particularly concerning as it leverages legitimate user permissions to execute malicious code within the context of other users' browsers. The flaw resides in the handling of the s4w-more parameter when processing requests to the wp-admin/options-general.php endpoint, where the plugin fails to properly escape or validate input before rendering it in the web interface.
The technical implementation of this vulnerability stems from a classic XSS attack vector where malicious input flows directly into the application's output without proper sanitization. When an authenticated user accesses the plugin's administrative interface and manipulates the s4w-more parameter, the system processes the input without sufficient validation or encoding, allowing attackers to inject arbitrary JavaScript code or HTML content. This occurs because the plugin does not implement proper output encoding or input validation controls that would prevent malicious payloads from being executed in the browser context of other users. The vulnerability operates under CWE-79 which specifically addresses cross-site scripting flaws in software applications, where insufficient input validation leads to malicious script execution.
The operational impact of this vulnerability extends beyond simple data theft or defacement as it enables attackers to perform a wide range of malicious activities within the compromised WordPress environment. An attacker with access to the administrative interface can craft malicious payloads that persistently execute in other users' browsers, potentially leading to session hijacking, credential theft, or redirection to malicious sites. The vulnerability is particularly dangerous because it requires minimal privileges to exploit and can be leveraged to escalate attacks within the WordPress ecosystem. Additionally, the attack vector is relatively simple to implement, requiring only that an attacker gain access to an authenticated user session and manipulate the specific parameter to inject malicious content. This vulnerability aligns with ATT&CK technique T1566 which covers credential harvesting through social engineering and malicious input injection methods.
Mitigation strategies for CVE-2015-4139 should focus on immediate patching of the WP Smiley plugin to version 1.4.2 or later, which contains the necessary input validation fixes. Organizations should also implement proper input sanitization measures at multiple layers including web application firewalls that can detect and block malicious parameter injection attempts. The security posture can be strengthened by enforcing principle of least privilege access controls, ensuring that only necessary users have administrative privileges within the WordPress environment. Regular security audits should include verification of plugin integrity and monitoring for unauthorized modifications to core WordPress components. Additionally, implementing Content Security Policy headers can provide an additional layer of defense against XSS attacks by restricting script execution sources, thereby limiting the impact even if such vulnerabilities are present in the application. The vulnerability serves as a reminder of the importance of proper input validation and output encoding practices in web applications, particularly within content management systems where user input is frequently processed and displayed.