CVE-2019-15837 in webp-express Plugin
Summary
by MITRE
The webp-express plugin before 0.14.8 for WordPress has stored XSS.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 12/11/2023
The vulnerability identified as CVE-2019-15837 affects the webp-express plugin for WordPress, specifically versions prior to 0.14.8, and represents a stored cross-site scripting flaw that poses significant security risks to WordPress installations. This vulnerability allows authenticated attackers with contributor-level permissions or higher to inject malicious scripts into the WordPress admin interface, which are then executed whenever other users view the affected pages. The flaw exists within the plugin's handling of user input during the configuration and management of webp image conversion settings, where insufficient output escaping and validation permits malicious payloads to be permanently stored in the WordPress database.
The technical implementation of this vulnerability stems from inadequate sanitization of user-provided data within the plugin's administrative interfaces. When administrators or contributors modify webp conversion settings or upload configuration files, the plugin fails to properly escape or validate the input before storing it in the database. This stored data is subsequently retrieved and displayed in the admin interface without proper context-aware escaping, creating an environment where malicious JavaScript code can persist and execute in the browsers of unsuspecting users who access the affected WordPress admin pages. The vulnerability is classified as a stored XSS attack because the malicious code is stored server-side and executed each time the affected page is loaded, rather than being reflected in a single request.
The operational impact of this vulnerability extends beyond simple script execution, as it can enable attackers to escalate privileges, steal session cookies, perform unauthorized actions within the WordPress administration panel, and potentially compromise the entire WordPress installation. An attacker could leverage this vulnerability to inject malicious scripts that redirect users to phishing sites, steal administrator credentials, or modify website content. The attack vector requires minimal privileges, as contributors and higher user roles can exploit this flaw, making it particularly dangerous in environments where multiple users have administrative access. This vulnerability aligns with CWE-79, which describes cross-site scripting flaws, and represents a specific implementation weakness in input validation and output escaping mechanisms.
Mitigation strategies for CVE-2019-15837 primarily involve updating the webp-express plugin to version 0.14.8 or later, which includes proper input sanitization and output escaping measures. System administrators should also implement additional security controls such as role-based access restrictions, regular security audits of installed plugins, and monitoring for unusual administrative activities. The vulnerability demonstrates the importance of proper input validation and output escaping practices in web applications, as outlined in the OWASP Top Ten security risks and the ATT&CK framework's defensive techniques for preventing code injection attacks. Organizations should also consider implementing Content Security Policy headers and regular penetration testing to identify similar vulnerabilities in their WordPress installations and ensure comprehensive protection against persistent threats.