CVE-2021-24488 in Post Grid Plugin
Summary
by MITRE • 08/02/2021
The slider import search feature and tab parameter of the Post Grid WordPress plugin before 2.1.8 settings are not properly sanitised before being output back in the pages, leading to Reflected Cross-Site Scripting issues
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Analysis
by VulDB Data Team • 05/03/2025
The vulnerability identified as CVE-2021-24488 affects the Post Grid WordPress plugin version 2.1.7 and earlier, presenting a critical reflected cross-site scripting vulnerability that stems from inadequate input sanitization within the slider import search feature and tab parameter handling. This flaw exists within the plugin's settings interface where user-supplied input is directly incorporated into HTML output without proper validation or sanitization measures. The vulnerability manifests when an attacker crafts malicious payloads that exploit the lack of input filtering in the tab parameter, which is then reflected back to users browsing the affected WordPress site. The issue resides in the plugin's failure to implement proper output encoding or sanitization techniques when processing parameters from the HTTP request, creating an environment where malicious scripts can execute within the context of a victim's browser session.
The technical implementation of this vulnerability aligns with CWE-79, which describes improper neutralization of input during web page generation, specifically in the context of reflected cross-site scripting attacks. This weakness allows attackers to inject malicious JavaScript code through the tab parameter that gets executed when users navigate to affected pages. The vulnerability occurs because the plugin does not validate or sanitize the tab parameter before incorporating it into the HTML response, enabling attackers to inject script tags or other malicious content that will execute in the victim's browser. The reflected nature of the attack means that the malicious payload is embedded within the HTTP response itself, making it particularly dangerous as it can be triggered by simply visiting a maliciously crafted URL.
The operational impact of CVE-2021-24488 extends beyond simple script execution, as it can enable attackers to perform various malicious activities including session hijacking, credential theft, and data exfiltration. An attacker could craft a phishing URL that, when visited by an authenticated administrator, would execute malicious scripts that steal session cookies or redirect users to malicious sites. The vulnerability is particularly concerning in WordPress environments where administrators may have elevated privileges, as successful exploitation could lead to complete compromise of the affected website. The reflected nature of the vulnerability means that the attack vector does not require persistent storage of malicious content, making it more difficult to detect and prevent through traditional security measures. Attackers can deliver payloads through various means including email campaigns, compromised websites, or social engineering tactics that direct administrators to malicious URLs.
Mitigation strategies for CVE-2021-24488 should prioritize immediate patching of the Post Grid plugin to version 2.1.8 or later, which contains the necessary sanitization fixes. Organizations should implement comprehensive input validation and output encoding mechanisms for all user-supplied parameters, particularly those used in administrative interfaces. The implementation of Content Security Policy headers can provide additional protection against script execution, while regular security audits of WordPress plugins should be conducted to identify similar vulnerabilities. Network-based intrusion detection systems should be configured to monitor for suspicious URL patterns that may indicate exploitation attempts, and administrators should maintain updated threat intelligence feeds to identify emerging attack patterns targeting WordPress vulnerabilities. Additionally, implementing principle of least privilege for WordPress administrative accounts and regular security training for users can help reduce the potential impact of successful exploitation attempts. The vulnerability demonstrates the critical importance of input validation in web applications and aligns with ATT&CK technique T1213 for credential access through web application exploitation, emphasizing the need for robust sanitization practices throughout the application lifecycle.