CVE-2021-24296 in WP Customer Reviews Plugin
Summary
by MITRE • 05/24/2021
The WP Customer Reviews WordPress plugin before 3.5.6 did not sanitise some of its settings, allowing high privilege users such as administrators to set XSS payloads in them which will then be triggered in pages where reviews are enabled
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Analysis
by VulDB Data Team • 05/27/2021
The WP Customer Reviews WordPress plugin version 3.5.5 and earlier contained a critical cross-site scripting vulnerability that exploited improper input sanitization mechanisms within its administrative settings. This vulnerability specifically affected high-privilege users including administrators who possessed the ability to modify plugin configurations. The flaw emerged from the plugin's failure to properly sanitize user-supplied input when processing review settings, creating an environment where malicious actors could inject persistent XSS payloads into the plugin's configuration parameters. These payloads would subsequently execute whenever review content was rendered on WordPress pages, effectively transforming the compromised administrative account into a vector for widespread client-side attacks. The vulnerability represents a classic case of insufficient input validation and output encoding, where the plugin failed to implement proper sanitization routines for data entering its settings management system.
The technical exploitation of this vulnerability requires an attacker to first compromise an administrator account or gain access to a high-privilege user role within the WordPress environment. Once authenticated, the attacker could navigate to the plugin's settings interface and insert malicious JavaScript code into configurable fields that were not properly sanitized. These fields typically included review display options, custom CSS settings, or other configurable parameters where user input was accepted without adequate validation. The XSS payloads would then execute in the browsers of visitors who viewed pages containing the plugin's review functionality, potentially leading to session hijacking, credential theft, or redirection to malicious sites. This vulnerability aligns with CWE-79 which specifically addresses cross-site scripting flaws, and demonstrates how improper sanitization of user input creates persistent attack vectors within web applications.
The operational impact of CVE-2021-24296 extends beyond simple script execution, as it enables attackers to establish persistent footholds within WordPress installations. When administrators modify plugin settings, they often trust the interface to properly validate inputs, creating a false sense of security that attackers can exploit. The vulnerability's persistence stems from the fact that once malicious code is stored in the plugin's configuration, it executes automatically on every page load where reviews are displayed. This makes the attack particularly dangerous for high-traffic websites where the XSS payload could affect thousands of visitors. The vulnerability also demonstrates how plugin developers must implement defense-in-depth strategies, ensuring that all user-supplied data is properly validated regardless of the user's privilege level. From an ATT&CK framework perspective, this vulnerability maps to T1059.007 for scripting and T1566.001 for credential access through social engineering, as attackers can leverage the compromised plugin to harvest user credentials and establish further persistence within the WordPress ecosystem.
Mitigation strategies for this vulnerability require immediate plugin updates to version 3.5.6 or later, which implemented proper input sanitization and output escaping mechanisms. Administrators should also conduct thorough security audits of their WordPress installations to identify any other plugins that may exhibit similar sanitization flaws. The remediation process involves implementing proper content security policies to prevent unauthorized script execution, establishing regular vulnerability scanning procedures, and ensuring that all user inputs are properly validated and escaped before being stored or rendered. Additionally, organizations should consider implementing web application firewalls to detect and block suspicious input patterns, and establish privileged access monitoring to identify unusual administrative activities that might indicate compromise. Security teams should also review their incident response procedures to ensure readiness for handling such persistent XSS vulnerabilities that can remain undetected for extended periods. The vulnerability underscores the critical importance of input validation in web applications and highlights how seemingly minor oversights in sanitization can create significant security risks for entire web platforms.